There's a lot of things I've heard are common then I ear they are uncommon. I'm not sure how common that is but I could see it being normal. Since your stomach gets upset a lot in early pregnancy, most girls throw up, but diarrhea would make sense. But make sure to drink plenty of water
First one I had intestinal cramps with diarrhea a couple of hours before preterm labour started, this one I had intestinal cramps and felt like I needed to but couldn't for a couple of hours before I lost my plug and contractions started. So for me, its common but everyone is different.
Yes it is but everyone is different and some ppl get symptoms that other have not just depends on the person