If you're unsure and are comparing it to a kick, then it's definitely not a contraction. Braxtons will often feel like a tightening but can also be painless. Kicks push outwards and are in small specific areas.
True contractions are painful. It may present as back ache, or a wave of tightening and pain that builds to a peak then eases off.
There's a very marked difference, and you will know when you feel it (also have 3DC) 