What is this pain? TMI

So I've had a pretty straight forward pregnancy now all of a sudden at 34 weeks I'm in constant pain. I woke up at 2am to a dull ache i ignored it fell back asleep then i woke at 6am with severe stomach cramps like bad constipation ran to the loo and it was diarhea. About an hour later the same happened again. Since and all day I've had a dull ache like I need to go to the toilet again but since this morning I haven't been able to go again. It's now 9pm and I'm so shattered but so uncomfortable is this a normal symptom or should I start to worry? Baby is kicking as normal and no other symptoms.