Help - Loss of Sex Drive

In October, my husband and I will be celebrating 8 years together and 2 years of marriage. We were high school sweethearts. The sex has always been great and exciting and there was a time when we couldnt keep our hands off each other. But I've noticed in the last 2 years or so, my sex drive has gotten considerably low, even more so in the last few months. He still touches me where I like but it doesn't feel the same - I cant relax or enjoy it. Sometimes I have to stop myself from physically cringing away. My brain wants it because it knows it's been awhile but my body doesn't. It's gone from a few times a week to a few times a month. I've been on the same birth control for 7 years, no new medications, diet hasnt changed but I have gained 20 lbs in the last 2 years. Could the weight gain be effecting me this much? I miss sex with my man and I know it kills him too because he has a MUCH higher sex drive, always has. Please, any suggestions or advice would be so much appreciated.