4 month vaccines and diarrhea?!?

My son got his second rotavirus vaccine at his 4 month visit along with the rest on the schedule. This was Friday. He started having some diarrhea on Monday but it was just 4 times and he seemed like he felt ok otherwise (no fever or vomiting or obvious upset tummy) so I didn't think much about it. Tuesday he had 6 episodes, and today (Wed) he's had over 10-15? It's not usually a lot at a time but it is mostly just liquid, sometimes basically a tiny squirt. Still no fever or vomiting. Still having wet diapers and eating ok. The main problem now is his bottom is raw and nothing is helping bc he may go again 5 min after I've slathered aquaphor on him. Was using desitin and triple paste but he screams with the zinc.. we let him soak in a warm bath tonight, next bath I will add baking soda to, but my questions are 1) what is the best thing you've found for a scalded bottom? And 2) has anyone else's LO had diarrhea like this after the vaccine? How long did it last? It's getting worse and not better and it's been 3 days 😣