Mixed signals?

I'm very confused. The last week I've been feeling off, a little like I do the week before I have a baby. This is a little TMI, but I've been having diarrhea every day this week, but at night I feel almost constipated. I feel like I need to go and have a lot of back pain. I'm only 35 weeks. Anyone else delt with this? I tend to have my babies early, but this is earlier than I would like. I have an OB appointment tomorrow and I'll ask my doctor then, but just thought I'd see if there was anything specific I should have her check on.