Struggling with A-levels

This isn't a question or anything, moreso a rant of some sorts but I'm worried about my education.
I've been dealing with depression and anxiety a lot for the past couple of years and it's making it difficult for me to attend my lessons because I simply have no motivation, and then I get too scared to go. I still try my best to keep up with my work, I've changed classes multiple times and even changed subjects (my original ones just didn't work out for me) and I was trying my hardest but I was just told that one of my teachers said "she [me] can kiss her grades goodbye."
I'm finding it hard to stay hopeful, not even my teachers believe in me anymore and no matter what I do I feel like as soon as I catch up I just fall behind again. I'm so lost and close to giving up completely. I've spoken to my head of year many times about how I feel but everything she says simply doesn't help, she doesn't understand how I feel.
I know it sounds insane, me complaining about something that I could "easily" fix but it just isn't that simple for me. I don't know what's stopping me. I don't know what to do