Exercise & Contractions

So I work out at least 6-7 days a week. Each cardio session I do AT LEAST an hr of cardio like running, jogging, jump roping etc. for some reason almost every time I do cardio I get contractions. Sometimes their mildly uncomfortable other times they are omg I have to stop and crouch down bc they hurt so bad contractions! I'm 9 months pregnant just about. Baby Luna is due in the end of May. Anyone else experience this ? Any tips ? Also what are some really good butt exercises I can do besides squats. I need something that I will see major results !!!!! So far I've only gained like 7-11lbs weight fluctuates but I just had my son a year ago and when I got preggo I was 10lbs away from pre pregnancy weight !!! I know darn it right !!!! Any tips / advice is appreciated ! TIA! 😘💋