I think I have ADHD, but I’m 20.

So I’m 20 years old and I think I might have ADHD. I’ve always struggled with school and am unable to complete many tasks. These are not my only struggles. My parents were against me getting tested for it when I was younger so I think I’ve learned to cope with it (not v well, I have lots of anxiety). I’m in college now and it’s REALLY getting in the way. How do I ask my doctor if I have it? How will he know? What will they be able to do for me? Any advice helps.