Sex during pregnancy help!

My last pregnancy I couldn’t keep my hands off my husband, especially in my second trimester! This time around, sex is absolutely the last thing I want. I’m 21 weeks, and we’ve only had sex twice this pregnancy. It hurts (Dry, penetration is painful) I can’t get in the mood, and I’m just miserable doing it. But I feel bad for my husband, he definitely wants it. He’s been very understanding and patient but I feel so bad, like I’m letting him down. Any suggestions?