Is it normal that i want sex more?

My boy friend and I have been dating for a year and a half. We are in love, this I am sure of. I know what it is like to be in a long relationship, I have an ex who I dated for almost 4 years. I am 20 years old and my boy friend is 23. My man treats me very well, cares for me, loves me in every way, always is telling me how beautiful I am and also spends lots of time with me, I see him everyday and spend the night at his house regularly. The only issue is that my boy friend has an extremely sensitive libido. It has always been like this, and it took lots of getting used to. It's like phases, sometimes he wants sex more often- anywhere from 3-5 times a week to only wanting sex when I ask (after about a week and a half of waiting). When he is in this funk, he often takes it very personally and offensively that I explain to him that I need to have sex to feel wanted. I miss being seduced. I love him so much, I just don't like having to cope with this. He has explained to me he knows other guys would want to have sex with me every chance they could get- but he just isn't in the mood sometimes. He explains it's work.. school, he is 'exhausted'. He even tells me that he feels incapable and feels unworthy when he can't give me what I want. Now, just so you know- it's not that he isn't responsive, he can get hard, just not in the mood. Is this normal? In my last relationship, my ex was the one who always wanted it- Now the tables have turned and I feel sexually unsatisfied and confused about why this is happening to me, and why he is the way he is. Has this ever happened to anyone else? Why do you think this is happening?? I'm sure there is no one else. I have tried everything (dressing up, foreplay, asking nicely, having talks..). I am tired of getting turned down by the man who is supposed to give love to me.