disappointing sex life

Is anyone else disappointed with their sex life? I love my boyfriend to death, but for the past 6 months or so sex feels like it's been a chore. Because of birth control, I have little to know sex drive, and nothing gets me horny. No matter what he does I just get frustrated or agitated. I need a solid 30 minutes of warm up. Even when I feel like I'm ready to go, sex is just mediocre. It doesn't even feel good. I hate that I feel this way and I feel so bad for my SO. He is always in the mood but I'm always turning him down. What do I do?!?!