So disappointed...

Last night, for maybe the third time since we've been pregnant, I actually wanted to have sex with my husband. I miss him so much, and I know he misses me. So we start having sex, and all of a sudden I go dryer than the Sahara desert and at the same time I start cramping so bad I had to make him stop... We couldn't even finish. My husband was so sweet and so understanding but I just cried and cried because for once I wanted to have sex and my body wouldn't cooperate. Has anyone else experienced this?