You gotta stop pressuring him and expect him to give into you. Just go with what hes comfortable with for now. And when hes ready hes ready. Just enjoy what you have for now.
Maybe something happened to him that he really doesnt want to talk about....like maybe he was molested when he was younger or it could be something thats sensitive for him to talk about. I know someone who was in that situation.
Put the shoe on the other foot. If he were pressuring you, wouldn't you be put off? Stop bugging him about it, let him know it's ok and if he doesn't want to. Putting pressure on him to perform is not helping the situation. Guys can't just get it up on demand, ya know. You are adding to the problem by pushing him, not helping. If it really bugs you that much and you don't want to just let things happen naturally at their own progression, might I suggest this is not the guy for you, miss hot pants? Maybe you need to break up with him and find someone interested in just sex.