Any thoughts?

This morning I was have super bad burning pain in my lower back for about 2 hours straight. I couldn't set for long and I couldn't stand for long. Just had to keep changing positions. But now it's gone. Any thoughts to what this is. Also, last night I was having some cramps in my lower stomach area and sharp pains in what seemed like my vagina every few minutes for about an hour. I'm 32 weeks.