16+4 weeks lower abdominal tightening

So I'm not sure if it's just me being overly paranoid/anxious, but I'm starting to get a tightening sensation in my lower abdomin/maybe uterus that feels like it's making a fist. It doesn't hurt by any means, though it's not necessarily comfortable. Naturally I went to Google & all it's telling me is Braxton Hicks or Preterm labor. I was just at the OB last week & everything was totally fine, so I'm not sold on the preterm labor. Though I feel it may be too early for BH..? Just curious if any of you ladies are experiencing or have experienced this, and if it's something I should inform my OB about.