I developed really bad agoraphobia in my second year of university. Same deal, passed first year (the problems were already apparent but I wasn't diagnosed, I was just "smart but lazy"). Once I got away from the partying and ease of first year I went into complete meltdown. I barely finished my second year, getting through by basically promising to take on extra work in my final year to make up for an entire module that I didn't turn up to. During this, my anxiety got so bad that I literally couldn't leave my house at times. Going out in public made me lose my mind, I panicked, my mind started racing, I was sure I would pass out at any moment. I was also extremely depressed during this period.

I had no help for any of this, since the doctor was basically telling me "I think you are bipolar but I can't help your anxiety, just face your fears I guess". Long story short, I switch doctors, I get diagnosed, I fail my third year and now have spent the past year off taking steps to sort myself out. Luckily, I have a family member who is ok with me living at her house rent free for the time being, although my family clearly looks down at me from time to time because "adhd can't be that bad". My solution has worked though, I've stopped doing things just because I felt I had to and my anxiety is something that I find very easy to live with. I am intending to get back into work and I'm trying to find something I'll feel comfortable with, but at my own pace. I don't want to have to lean on people my entire life and completely intend to get a job and a flat with my girlfriend in the near future, but you have to do these things on your own terms.

As far as advice, I would say "I am scared to take my meds again(Concerta 36mg) because I feel that they exacerbate my anxiety" is telling of the mentality you've developed because of your anxiety. I know people will say "you're fine just realise that" as if it will make it go away and it's not that simple, but actually changing the way you think is a big part of CBT and will contribute ( of course, it won't immediately or completely fix your anxiety). You have to take a step back and see what you're worried about from another perspective. Did the meds help before you were off them? If they did, then what you are worried about is the rise in heart rate etc causing you to be more anxious. I am aware that when you are in an awful anxiety ridden place, these words seem empty, but you have to remember they are just symptoms. The consequences if you fail are not the end of the world, you will not die from a panic attack, nobody is going hate you because you are struggling and anyone that judges you for asking for help is not worth the effort of your thoughts.

Seriously, my best advice is just take your time and do it how you feel comfortable. Talk to someone at your school and say you need help. Talk to someone about your anxiety and see if you can get an additional medication to help with the anxiety side effects. If you have to take extra time to pass, take extra time. You are not obligated to do any of this stuff and surely nobody needs to have their emotional wellbeing ruined over a few missed classes and staying on the honor roll. If your parents are going to judge you with full knowledge of your ADHD, then perhaps talk to a psychiatrist instead. It helps a lot to have someone on your side who you can talk to. Of course, I don't know your parents, but us anxiety and depressed types tend to believe nobody will understand us when we are in a bad way, and then realise after that if we asked for help we could have got it. Perhaps tell your parents your difficulties. It's hard to understand whats going on if the first they know of your problems is "I failed some classes". Let them know you're struggling and if they aren't sympathetic talk to someone else.

Hope this helps a bit, sorry for the wall of text. Hang in there and I'm sure you'll be fine. :)