tightening is lower abdomen

I'm not sure if what I'm experiencing is contractions or not. I've been having a really tight pressure like pain in my lower abdomen. It'll last for about 20-30 seconds and then it's gone. The reason I'm unsure if it's contractions is because I tend to really only notice it when I'm laying on my side. Maybe a couple of times while sitting. It makes me wonder if it's just how my little boy is positioned or how he moves when I'm laying down. I'll have some occasional tightening in my abdomen while I'm standing but it's NOTHING like when I'm laying down. Laying down is much more painful. They feel like they could be contractions but I always thought contractions happened no matter what position your in, I find it weird I  only really  notice it while laying down. (This is my first baby) I keep hoping it's contractions because I'm ready to get this show on the road haha. But I don't want to get my hopes up either. Anyone else have anything like this happen toward the end of their pregnancy?