Is sex such a crime?!

So about a year ago I was in my prior relationship and I had to end it because she could go MONTHS without even thinkin about having sex. Its almost like as if she was asexual, not that there is anything wrong with that but I am a human being and I need that attention every so often just like most of us. Nothing aroused her, nothing turned her on. If we did happen to have sex, no lie, it would last THE MOST 15 minutes. 15 mins is just getting me started! I went from my ex that we fked for hours at a time to this one who barely gave it up for 15 mins every 2 months or so AFTER i would start an argument over it. I felt like I was in a friendship not a relatioship. Im not a sex feen or anything but I do like to have a sexual relationship with the person I am involved with, is that a crime? So after i ended it with that one i found this amazing woman. She and i hit it off great. Conversation was amazing. SEX WAS AMAZING. Finally i thought i found someone worth being with. Maybe I could have been wrong. I been with the gal for 9 months. At first everything was great. I MEAN EVERYTHING but as time passes by it just seems like im back a square one. Sex is great overall but its boring. Really boring. Same sh!t different MONTH lol I know its not me thats the problem because i KNOW my stuff when it comes to that. Trust me she finishes multipule times when we do do it but after its over...she just rolls over and falls asleep. I already mentioned it to her about it twice. She got upset n all but like i said i dont want to be in a d@mn friendship!!! I want someone who desires me like i desire them! I dont understand what the problem is. From all the girls that practicely throw themselfs at me i dont see why i choose the least active ones. Ugh! What am I doing wrong?