First of all, there are good reasons to trust trained professionals and a diagnosis over anybody else.

On topic: I'm diagnosed with ADHD and have not much issues with eye contact. It's usually a conscious behavior for me.* I do a bit of eye contact and look away again, mostly with people I just got to know or when talking to people without an interesting topic. I do this delicate, but very conscious 'yes-I-make-eye-contact-bot-not-too-much-so-you-see-I'm-interested-but-not-a-creep' thing.

On the other hand I stare into people's eyes when in a discussion I'm interested in and/or they have something interesting to say.

*I will be checked for ASD later this year.