Ay, first time mom anxiety, alam ko yan! At 26 weeks, slight loose stools or changes in bowel movements are actually pretty common kaya wag mag-alala, maraming preggy friends ko nag-experience ng ganyan dahil sa hormones at ang prenatal vitamins, lalo na kung may iron. But if it's been going on for a few days, you're feeling crampy, or may blood or mucus, I'd definitely ask your OB about it para sure lang, kasi sometimes it could be something they need to check especially since preggy ka pa.