Def call your doctor because those are “signs of labor.” But, like you said, pregnancy is weird :) they might just tell you “it’s normal.”
Could it be Braxton hicks? I’m 35 weeks and I’ve been having loose stools, experienced Braxton hicks since 28 weeks and having lightning crotch. Last night, I had all 3 but it went away with a heating pad especially with Braxton hicks, it helps.
If the cramping continues for more than an hour and has a regular pattern, I’d definitely call your doctor! Braxton hicks will typically stop if you get up, drink water, pee, move around etc. and don’t follow a pattern but they can definitely feel period-ey. Diarrhea is definitely a early sign of labor/late 3rd trimester thing so that shouldn’t be something you should be too too worried about!
I always err on the side of calling your dr office since they know your case best & can advise. It could be a number of factors, and loose stools can also be indicative of dehydration, which can lead to preterm labor, so getting checked out & ensuring adequate hydration are safe ways to address anything that may seem off or unusual.