Hi! First of all try not to be nervous! I know it’s easier said than done (for me at least!) but you can only control your actions and feelings. I understand the worry, but try not to let it overwhelm you! If it helps, I believe that a majority of medical professionals are in the field because they genuinely want to help others. It’s hard to put in the immense amount of work that it takes to get a medical degree if you don’t (I’m currently studying cognitive and behavioral neuroscience and I’ve seen those kinds of people drop like flies).
Controlled substances like Concerta can only be prescribed by certain medical professionals. Obviously I don’t know what qualifications your GP will have, but they will probably have to refer you to a psychiatrist for treatment/medication. If you find yourself with a doctor that needs “proof,” they might/should be able to access a record of you being prescribed Concerta because of its status as a Schedule II drug. Usually records of prescriptions written for schedule II drugs are kept in state databases.
I understand where the worry comes from and how hard it can be because I dealt with doctors not believing me when I was a kid. I cycled through more doctors than I can count, but I eventually found someone who listened. If I had given up after the first couple doctors refused to believe me, I don’t know where I would be today. I genuinely believe that if you describe your symptoms and your experiences to your doctor and they flatout don’t believe you and require you prove you are being genuine, they are the problem, not you and they aren’t worth your time.
Long story short: Someone will believe you even if the first doesn’t!