Why doesn't my girlfriend want sex as often as I do?

Some women just dont get in the mood as often, I love my bf and I think he sexy, but sometimes I can go like 2 weeks wqithout really wantign it or being in the mood. It isn thim, Its just me, not being in the mood for it. Women do have lower sex drives than men, men need to be horney to *** (to procreate) where its not necccessary for women to be horny to procreate. Its just a natural gender difference, dont take it personally!