My 2 year old is not going to the toilet well, watery poop but she complains about the sore stomach, its been 3 days and she vomited on day 1 once?

Immediate exam: You must rush your 2 year old to a medical clinic for a complete evaluation immediately. Your child may have an infectious illness or some other illness which demands immediate treatment. The sooner your child is properly evaluated and treated the better the chances for a full recovery. Because of the young age of your child I suggest an immediate evaluation!