Hello Dr. Rynne-I Have A Big Concern For My Son

Hello Dr. Rynne-I have a big concern for my son (32y/o)has a 2 wk hx of sinus/ear infection-went to an Urgent Care-rec'd ATB/steroid. He finished steroid- ATB-took x4-5 days-(GI upset-he should have finished/taken probiotic) Approx 5-6 days later developed (gingivitis) red/sore lower gum with pus! (never had this before) Lab Tests at Urgent Care- Neg. for Streph/Influenza.
Sat. 12/17-lips swollen-mouth very sore-woke up Sun 12/18-had white patches in mouth/tongue/few blisters in mouth/tongue-(I advised ER/Urgent Care-all OTC/meds) Urgent Care MD-prescribed new ATB-he was then diagnosed with: Hand-Foot-Mouth Disease-(his 4yr old is asymptomatic) he has 2 dogs-and has excellent hand washing skills! All this
week he has had white coated tongue with blisters and his lips/tongue have some ulcerations to them! He is a Police Officer and is refusing to go back to see MD. I am very concerned it may be Steven-Johnson Syndrome-he says-I worry too much. I worry because he wants to"let this run its course. He says he is trying to keep hydrated-excrutiating pain-apparently has high tolerance. Please advise! Thank you! Margaret