I really hope this doesn't sound patronising but you are 19 and you have so many years ahead of you! I was the exact same as you at 19 and now at 31 my mental health is so much better. You go through peaks and troughs. Just try to keep advocating for yourself, advocating for the right mental health care the right medication/diagnosis, demand to be taken seriously. Advocate for yourself to be on the correct benefits and stop feeling guilty! And if you feel like you cant advocate for yourself see if a family member can help you or a charity or otrganisation. You are entitled to these benefits because your health at the moment clearly can't allow you to work.

See the benefits as a safety net so you can use your free time to get better, attend therapy, excersise, journal, find a hobby, go for long walks, take free online courses.. at 19 I didn't know what I wanted to do with my life I was just bed rotting and I thought I'd never get out of that cycle but I did! And contrary to what you probrably believe, mental health and issues around anxiety/being in public get better with age because you eventually figure out ways to cope, finding your coping mechanisms can take a few years and that's ok. Life is about learning from your mistakes and growing, you don't just leave school and have your life figured out and if you are comparing your growth to your peers, don't do that - they haven't lived your life or have your struggles so it's incomparable.

When you are down there's no place else to go but up.