3month old has bad diarrhea

Hi ladies my 3month babygirl has been having horrible dirrehea I mix feed because I don't really have milk and I recently changed her formula to S26 and she still has it💔 I recently took her to the emergency room and I was just prescribed probiotics and fever medication but the dirrehea continues iv changed my diet iv tried everything I feel could be the possible problem it's been 4days😔anybody had a similar problem and managed to solve it? I'm desperate😩