boyfriend's low sex drive

Any girl ever been in this situation? When your sex drive is higher and just ended up wanting it so much. I discussed it with my boyfriend but he always gets mad about it. I'm just confused because we've been dating (only) for 11 months, I know it's not that long-- but the first months or at least the 8th month he was all excited but these past few weeks we only have sex once every two weeks. There's no major changes in his life that I know (work stress, etc). This might sound selfish but this is really messing with my self-esteem a lot! How you girls dealt with this, help me out :(