Arousal Probs

Whenever my boyfriend and i are in bed, i get really lazy and i just lay there and don't feel like giving to him. I feel so selfish and i don't want to be. I want to please my boyfriend and make him happy too but it always seems so difficult for me. And then it turns him off when i just lie there and he gets upset. But i do pleasure him; just not as much as he does so to me. All i really do is give him hand-jobs though because i got raped when i was younger so i'm scared/uncomfortable giving him a BJ. Is there anything i can do to become more sexually active? Also, he just told me tonight that he has been losing interest in pleasuring me the past few months but it hit him tonight that he just doesn't like to. Before he always loved to pleasure me. It turned him on and he liked it. Do you think part of the reason could be because i don't give enough to him? Maybe he's just so tired of putting all his energy and effort into making me happy. I have one more question. We just started having sex but whenever it comes time to do the deed, his penis goes limp like it's not interested. But he wants sex. He has a desire to but apparently his dick doesn't. I try to get him worked up but it just doesn't work. We can only get it semi-hard and then it dies. Even when we'll get it in, it goes limp and falls out. Is there anything else we can do besides go to a doctor or him go on some sort of medication? Is there something else we could try? BTW: We're only 18. Please help me out. I'm so confused and both our self - esteems are decreasing.