There’s lots of great comments here, especially pointing out that the “problem” may lie with his anxiety/neurodivergency more than specifically whether or not he’s on the ace spectrum. There’s just a couple things I want to add, just in case you haven’t thought about it before. Obligatory, I’m not a doctor or relationship expert, I’m just an idiot on the internet giving my two cents based on one post about your relationship. You guys know yourselves best

Regardless of whether or not he’s ace, making you feel like a creep for wanting sex is a communication issue. He should not be making you feel like that. Think about it like this. You would never call him broken for not wanting sex right? You don’t think he’s messed up, you’re just trying to understand him right? You don’t want him to feel bad for how he is. But he is making you feel bad for wanting sex, which is perfectly normal and okay thing to want from a romantic partner. If you were demanding sex it would obviously be a problem, but there’s a difference between communicating boundaries and making you feel like shit. He’s well within his rights to say “hey, sex makes me uncomfortable and I want a non sexual romantic relationship with you. Please do not try to initiate sex or talk about sexual topics.” But making you feel like a creep is kinda shitty. If it makes him uncomfortable then he needs to talk to you and you guys need to establish clear boundaries. If he avoids those conversations then he’s forcing you to guess where his boundaries are. That’s not good for either of you

It sounds like you want him to think about if he’s ace/greysexual bc you’re looking for an answer for what’s going on bc you feel like it’s your fault. Like you’re not making yourself attractive or desirable enough for him. Ace/greysexual are just labels that help us describe how things are. So rather than focusing on the label (since he doesn’t seem eager to explore labels for himself) just focus on what he’s described. He said he doesn’t like genitals and rarely thinks of sex, which sounds pretty similar to someone on the ace spectrum that’s sex averse. So if its easier for you to think of him as on the ace spectrum for your perspective of feeling undesirable the I think it’s okay to do that. Obviously don’t try to assign him the label by calling him ace if he’s not comfortable with that, but if in your brain when you feel undesirable, you remind yourself “he just doesn’t/rarely feels sexual attraction. It’s just how he is” I think that’s okay to do

Also, if you haven’t asked him before, I would ask what he was feeling and what motivated him to have sex with you the few times he did. You mentioned once was when you had brought up him maybe being ace and he got upset and then you had sex. I would ask if he was actually in the mood for sex or if he just felt like he was supposed to. If he was actually in the mood then I would explore what about that moment caused that. If he wasn’t though, then explore what made him feel like he was supposed to be. Is it a matter of his masculinity, that he feels like a “real man” should want sex? Was he just trying to avoid the conversation? Did he feel guilty towards you? Exploring some of these questions could help you guys come to a better understanding of each other

I also want to say this, just so you’ve heard it: I know you said you love him and would never leave him, but please remember that a relationship doesn’t have to be romantic to be important and loving and intimate. It sounds like sex is fairly important to you in a romantic relationship whereas it doesn’t seem to be for him. That’s okay. You two can love each other and care for each other and still be best friends without being in a romantic relationship. And removing the romantic part—and therefore the pressures of wanting sex or to feel desirable to him—could make the rest of the relationship smoother. I just don’t want you to think that your relationship would lose value or love if you were no longer romantic partners or for you to think you’re “giving up” on him or the relationship. If you want to end the romantic relationship, you would just be changing the nature of your relationship, not breaking it off completely. Again, I just wanted to say that to make sure you’ve heard it from somewhere or someone

For what it's worth, if you think your partner is neurodivergent, there are potential things there that can drastically affect how he feels sexual attraction. Maybe he's ace or somewhere on that spectrum, but given that he seems eager under other circumstances, I'd say it seems more likely that a combination of anxiety and neurodivergence (especially ADHD) can result in the behavior you're seeing. This article mentions that sexual aversion is over 10 times more common in people with ADHD.

The other tricky part is that sex can be an incredibly anxiety-inducing subject, which might just make him shut down when trying to talk about it. Instead, I'd gently try to talk to him about neurodivergence and see how he responds. If he can talk to a good professional about it, that would likely be a great place for him to start figuring out some of this stuff, and deal with his anxiety (and whatever other feelings are bundled up in this) in a healthy way that will allow the two of you to communicate.

If he's averse to therapy and thinks he must be "broken" to seek a therapist, try to encourage him--seeing a therapist is more like having a personal trainer than seeing a surgeon. A therapist talks in terms of goals and growth.

So, it seems like your SO is experiencing some issues related to his anxiety, and is dealing in a less than optimal manner. (Obligatory Not a Doctor statement)

However it does seem like he might be somewhere under the Aro Ace umbrella by your description.

You mentioned doctor, is that a psychologist/psychiatrist? Because they don't seem very supportive.

There might be no easy way to bring up the issues in the relationship, and it sounds like he needs to make some more progress.

It could beneficial to get him to speak with another Ace person, face to face.

Or (and this is a risky method and not recommended) just start sending him ace memes that don't flat our say they are ace memes.

Oh, and please be safe and have some garlic bread.

There's a lot to unpack here and I don't feel qualified enough to help you with that.

The fact that he feels "disgusted" by genitals and doesn't think about attraction at all, I think, clearly points to the Ace spectrum. When you talked to him about it, did you tell him what you've written here?

I will never leave him, I love him, he's so good to me. I'll take a dead bedroom to stay with my best friend, but...

You told us that he suffers from severe anxiety. Maybe he doesn't want to explore the idea because he feels it might negatively impact your relationship, maybe even lose you. But this isn't about you deciding if he's worth it or not, nor is it about you trying to "fix him", but finding ways to make the relationship work despite your differences.