Contractions?

Not sure if I’m having contractions or just typical third trimester pains. I’ll be 36 weeks this upcoming Tuesday. Today, since I woke up I’ve been having uterus tightening, along with intense constant back pain. Every now and then i get crampy period pains. Only thing that’s constant is my back pain, the contractions and period pains are sporadic. I woke up feeling extremely nauseous this morning and just haven’t quite felt like myself today. I’m a first time mom so I have no idea what is normal for early signs of labor or just typical feelings for being this far along.