First of all, there's nothing wrong with wanting to have sex with your partner, and it's normal to feel hurt or disappointed when he rejects your advances. How you handle it matters, but I don't think you're being too sensitive and I don't think you should feel guilty about it. His age might have something to do with it, but stress could also be getting to him. Both of you living with your parents can complicate things as well. My guess would be he really doesn't feel like he can perform right now.
I used to have a similar problem with my boyfriend. We're both 33. For a few months, I was worried my drive might be higher than his or he might be less physically attracted to me. I quietly agonized about it for months until I just couldn't take it anymore and had to ask what was up. He explained that he was never this sexual in his previous relationships so he thought because it was more than he was used to, we were doing it a TON. I don't need to go into that, but it explained a lot. We live together now and we're having sex a lot more often.
I think you have to ask him as nicely as you can. You don't want him to feel like he's letting you down, but he needs to know that sex matters to you and that it's important for you both to be happy.