Blood in sons stool

My son is 7 months he somehow caught a virus and had a fever of 103 with diarrhea. The fever went down but his diarrhea hasn’t gone away. I’ve been putting Desitin after every change but his bum is still extremely red and I noticed after his last change he has a little bit of blood. I’ve took him to the clinic and the ER and all they can tell me is just for him to ride it out with Tylenol/Motrin and some Pedialyte. Is there anyway I can help the redness ease off and prevent blood. I feel so bad that he’s going through this.