My daughter has had diarrhea for the fourth day in a row. It's either her…

My daughter has had diarrhea for the fourth day in a row. It's either her teeth or some kind of infection. She has watery stools for two days now and also had a little bit before bed (photo ??). She's become very fussy, like she doesn't have a fever but I measured it every time. She keeps asking for cuddles. It's running down her chin. Everything is going into her mouth. She doesn't cry, but appetite seems to be gone. What could this be? And why is this happening? If it's her teeth, isn't it too late to do something about it? How can we find out for sure?