Diaper rash HELP !

Brittany • Christian Mother , & wife ,baby number two Due march 27th??
Hey mamas , I need some insight . LO developed a rash over the weekend .. At first i thought it was just a regular diaper rash because he pooped in his sleep . so I was using desiten on his bottom (it's on both cheeks )  however that hasn't been working , I'm guessing it a yeast rash ? But it feels like it has heat in it , and it looks kinda scaly (like a sun burn) it has little red bumps all grouped together . Now I noticed tonight it's spread to his little peepee area . I'm hoping his doctor can see us tomorrow ! I've left a diaper off of him ? Any insight on what it sounds like ? I feel so bad ! I've tried everything , but nothing is working ?