You'd probably be better off hearing from my own partner about this but they don't have lemmy so I'll do my best. This really is just something you HAVE to candidly talk about. It can be difficult when you are young and when your relationship is young because emotions are higher but letting yourself be sexually uncomfortable to please them is unhealthy. It's bad for your relationship and will lead to you feeling uncomfortable with them as you might already be feeling. I've been on the receiving end of this and eventually becomes clear that something is off. They can probably tell or will eventually that you aren't as into it as they are and might blame themself. Having to question whether your partner finds you attractive or wonder if you are just bad at sex can really damage the ego. Talk to them so you don't have to put youself through sex you don't want and so they don't blame themself for you not wanting sex. Communication is everything in a relationship.