Contractions or ???

So I'm a FTM. I'm 38w1d and I've felt what felt like menstrual cramps so I'm assuming those are contractions. I also felt something which I'm pretty sure are contractions. They weren't like menstrual cramps but they were definitely in my uterus and I had to pause what I was doing for a second. Today I've been feeling what is kinda like gas but not in my stomach, it's like coming by my butt. I've tried to go to the bathroom but nothing will come out so I'm unsure if these are contractions too, just pressure from baby's head being so low, or what. Anybody have any insight?