Twingey, period like crampy things lower abdomen and back....

I’m 18 weeks pregnant and have been having these twingey, period like crampy things in my lower abdomen and back.... it feels almost like I have a brick in my bladder like when you have a UTI but it doesn’t hurt to pee so I don’t think it’s a UTI. And TMI but sometimes it also feels like I have muscle cramps like in my butt hole...... Should I be concerned about like early labor or something?? I read if you get pregnant again before 18 months after giving birth you’re more likely to have pre term labor.....anyone else heard of this or is this pain normal?