could this be labour?

So I'm 37 weeks, had sex this morning, he didn't cum and didn't orgasm, we stopped after a few mins cos he didn't like it.
Now I've been on my ball and walked to the shop, now feeling pressure and period pains down there.
Should I start timing it to see if its contractions or braxton hicks? Also how do I time it? It went and now it's back! No waters braking and no bleeding!