I felt BHs as a tightening (and later a hardening) over my belly, especially at the top, whereas contractions were much lower down within my pelvis. With both pgs I had what I later realised had been contractions from about your stage, but went on to deliver at 39+3ish and 41w.
If you're feeling OK otherwise, I doubt it's something to worry about, but, as ever, mention it to your midwife at your next an checkup.