I know what you are thinking....you think that maybe you did something wrong or he isnt attracted to you or doesnt find you sexy etc. but don't fear. Im sure this has NOTHING to do with you and what everyone else said is right..... it's probably stress, nervousness, thinking about something negative or any other list of possibilities not having to do with his feelings for you. I've been in your shoes before. Dont let this bring you down. Keep doing what you are doing and try not to let this inhibit your sexuality or desire.