Early labor??

I’m 36 weeks with baby measuring 3 weeks ahead consistently. I’ve been having very painful menstrual like cramps since 7 last night. They are not frequent however, there’s like 3 to 4 and hour but that last for a while. I’ve been throwing up since yesterday, can’t even keep liquids down now. I don’t wanna waste a trip to the hospital if this is normal end of the road pains but I’m pretty miserable now. I have the strong urge to push when the cramps happen so how can I tell the difference between baby pains or poop pains??