I Believe My 14 Son Has Diabetes, His Doctors Appointment

I believe my 14 son has diabetes, his doctors appointment is not for two months. I'm too nervous to wait that long.
He has a tan like strip in his neck crease, noticed it about a yr ago and its only gotten thicker. Looks like dirt but not.
He has excessive water gain. Pushing on his fingers, arms. Anywhere feels like a balloon.he is obese and has only started gaining all this wait when I took him off his last adhd meds. (he blacked out after being on them for a month)
He has a nasty yeast infection in sure on his neck/chest area.
Drinks more fluids than food.
Please tell me, should I insist on being seen sooner for his issues?
I know the rash needs to be treated. I've been trying. He says its been there forever. I say a month maybe two. I've been using an antifungal cream last two days and it seems to be going away finally.