Can I refuse to take off my clothes during a physical exam?

I am 14 and have a physical exam sometime next week. I have self harm scars and cuts covering the majority of my body. Can I refuse to take off clothing? I have extreme (diagnosed) social anxiety and this terrifies me. Like, I’m going to kill myself if I have to take off clothing kind of terrified. What happens if I refuse? Can I refuse? I might tell the doctor why I refuse to take off clothing but I just can’t physically take them off. Thank you.

Edit: I currently see a therapist and I see a psychiatrist on Friday, so I am getting proper help.

Double edit: it’s not the undressing itself I’m scared of, it’s about the person seeing my scars and cuts and let’s just say it’s pretty bad... I don’t want them to tell my mom either. She knows but thought I got over it awhile ago. It’s the worst on my thighs, on both and all the way down. There’s also a ton on my stomach and left arm. The reason I’m so worried is because they said to wear loose clothing.