If you feel they are real contractions, time them. BH doesn't have a pattern. Also, real contractions will become stronger, more painful and more frequent no matter what you do. Walking or switching positions won't relieve them. Once they are about 5 mins apart and not stopping, go in :) you've got a few weeks left still and I'm sure it's nothing. I've had awful period like cramps with my BH too since about 36 weeks and im a day past my due date! Lol.
When you begin to notice a pattern and they're accompanied by other labour symptoms (ie bloody show) then call the hospital and explain what's happening. That's what my midwife told me to do as I'm coming towards the end of my pregnancy as well.