Dealing with Doctor's Appointment Anxiety

i have a lot of anxiety about going to doctor’s offices, and my father just told me today that i have an appointment this afternoon that i was not aware of before now. does anyone have any advice or coping skills that help them get through the experience in general? i’m going in for a check up on my chronic recurrent multifocal osteomyelitis. specifically i hate being touched by people i don’t know and the doctor’s office is completely unpredictable; for example, i don’t know if i’m going to get an x-ray today, if i need an mri set up or if i’m getting my blood drawn. I don’t even know what the doctor is going to ask me ahead of time, i literally am so anxious right now. i can’t tell the doctor to be more aware of my needs because i don’t have a professional autism diagnosis (i am on the waiting list and i have a referral for one), i just don’t want to say that i do and then not have any evidence to back it up or for him not to believe me, so i don’t think i’m going to say anything. my father is going with me to the appointment, which is good because i would literally rather wither away than do this at all. i’m also changing hospitals after this appointment and it’s really freaking me out a lot. Does anyone have any advice?