Contractions

I’m 36 weeks, my husband & I went to the store about an hour ago when he got off work to get somethings for the week.. it’s 4am where I live. Anyways, besides the point, I’ve had cramps off & on all day, nothing that I’ve been concerned about. Well, at the store my belly was really tight & it felt like my daughter was putting all her weight on one side, my right side to be specific. Once I got home to sit down, it continue to be tight & I was just really uncomfortable.. Now I’m having cramps off & on but some are in my back, some will go through my sides. My stomach isn’t tight anymore, does your stomach always get tight during a contraction? Also, I had a lot of pressure while walking around the store.. not sure if this is early labor, I have had the feeling all week that she’s gonna come very soon.. I’m due October 31st, but don’t think I’ll make it til then..