How much time do you spend together when you aren't working/at school? How well do you communicate about other aspects of the relationship?
I think you need to follow Wondergirl's advice and make certain you have interests and things to do (not work or other obligations such as college) that give you time away from each other.
Do the two of you go out together? Do you still 'date'? If you don't, ask him out. 'Dating' shouldn't end just because you are living together.
How well do you communicate with each other about sex? I don't mean frequency. I mean fantasies, likes, dislikes, positions, toys, sharing erotica (including porn), etc. Do you flirt and tease each other when neither of you is expecting sex?
Look at how much emphasis you are putting on sex. Are you wanting it because it feels good and you want to have fun with him or are you pursuing it as a way to affirm he cares about you and wants you? If you think he feels like it is a 'chore', how do you really feel about it?
You've tried talking to him about how you feel. Try backing off (pressure to have sex can be one of the biggest limiters) for a few weeks. Then before bringing up emotions, share your observations on the relationship and sex. Ask him what he thinks. Ask him if he remembers when the last time he initiated a kiss or sex was. Ask him to think about the relationship and what he needs in it. Ask him if his needs are being met. Share your needs. If he is making you feel 'stupid' for trying to communicate, then tell him that he may not mean to but he is adding to the issues. Listen to each other and see if together you can find ways to improve the relationship. If you can't, then you have to decide if this is the relationship you want to be in.
If it isn't enjoyable for you, definitely back off and do things that are.