ladies help

I never post on here !

so ive been with my girlfriend for about a year now.. and I love her to bits.. she's the best I ever had and I wouldn't trade her for the world. but I'm having a problem... I really have to beg for sex.. like really beg.. maybe like once every three weeks she will initiate it.. but thats if I'm lucky..when we do have sex its a very loving expirence..I always make sure she finishes first.. I am a pleaser so I wont stop until she finishes .. I would never cheat on her so that's out of the question.. like I said she's the best thing that has ever happen to me. I just get so frustrated sometimes..but I don't show it..I have a very high sex drive and I can make love to her for hours without loosing stamina. and the fact that I really want to give her a baby doesnt make my problem any better... ive never had this drive for anyone else.