Contractions/BH or just baby?

I *think* I’ve been having contractions, however I don’t know how to tell the difference between BH and regular ones? They’re not regular or anything but it is now into my back pretty bad where there’s a constant dull pain. when I try and walk, i do feel my stomach tighten but that almost feels like the baby stretching out?? I’m only 28 weeks so I am chugging water and hoping for the best