Loose stool and mild diarrhea in Third Trimester

Hi, may I know when you started having loose bowel movements in Third Trimester? I just entered Week 31 and have been having diarrhea first thing in the morning. There's no other discomfort so it isn't food poisoning. I read that this is the body's way of preparing for labor, but is Week 31 too early? Thank you! #1stimemom #advicepls