Contractions?

I am out with my husband and his family today trying to walk. So we went to an outlet mall. Well after we ate dinner and drove about a half an hour I started getting this tightening sensation at the top of my belly that lasts about 20 seconds or so. It's irregular so I don't know if it would be a Braxton Hicks or not but it's been happening for about 20-30 minutes or so now between 3-7 minutes. It's very light sensation. Just wondering what you guys think it could be. I also started getting constant back pain around the time they started.