I can relate. I'm 23 and I've suffered from depression my whole adult life.
I studied photography for less than a year at Glasgow School of Art in 2012/13 before leaving because I was so damn depressed.
Since leaving I had been working part time while working on myself. I have matured a lot since then, even if my depression and anxiety remains. In regards to depression, I found it helped a lot to keep a notebook beside my bed, and writing down something positive every morning and every night, without fail. I've switched anti-depressant medication 3 times but the side effects were too prominent for me and i've resorted to just trying to cope in other ways. It can work for some people though, so maybe you should talk to your doctor.
It sounds like I suffer less than you from anxiety, but interviews and speaking in front of people make me extremely nervous and my hands start visibly shaking and I start sweating sometimes. My doctor prescribed me a very low dose (2mg) of diazapam, which I take ONLY in highly anxious and important situations. Please note it's important to not take this too frequently as it is highly addictive and it will make you even more anxious when you're not on it, if you overdo it. Nevertheless, as long as you do not have an addictive personality, I would highly recommend this, especially for interview situations.
After 3 years of working on myself and my art, I decided it was time to go back. I began working on my portfolio last November, applying for several art schools, and I just finished my last interview a few days ago. Since last Nov, I pushed myself to the limit to make a great portfolio, and it has finally paid off – i've received 3 unconditional offers so far and still to hear from one more school. I used to have frequent existential nightmares since leaving education, but they have stopped now. I feel like i'm back on track, and I hope you will get through your problems too so you can feel the same way.
To conclude, people like you and me have to work extremely hard to get to where we want to be, much harder than people without our issues. We have to prepare twice as much for interviews and presentations, push ourselves harder than others to get things done, and unscrupulously organise our time so we are productive. But take it from me – it is worth it. The biggest lesson i've learned is to look at failures as a learning experience, and not let them hold you back.