How do I include that I've been too sick to be in school on my application?

Hey everyone. Super stressed, no clue what to do, so I figured I’d ask.

I’m 19 currently. When I was 16 I developed pretty severe mental illness. I couldn’t go to school for the last 6 months of my senior year, but did end up graduating by doing coursework at home with pretty good grades. My goal was to study abroad and I got accepted to a really good school in europe, so I decided to go. Unfortunately, the first year I was there my illness got really bad. I couldn’t even complete my exams. They allowed me to try again for a second year, but when I couldn’t attend class or my exams again in december, they gave me the choice to either immediately start fulfilling my duties as a student, or withdraw. I couldn’t do either, so they chose the latter for me.

Since then, I’ve been back home and working full-time on improving. Going to see doctors and counsellors and groups, and trying new meds. Eventually, things actually started to improve, and as a little “test” for my improvement, I decided to do a short language course abroad, just to see that I can be on my own again, and attending class. I’ve been here for over a month, and I’ve never felt better in my life. So long I’ve been fighting to improve, and I guess it just took the proper support and medication and I’m finally healing.

I thought it was too late to apply to be back in school for the fall, but I literally just found out that the school here (HKU) is accepting late applications until tomorrow. I love everything about being here, and I can’t believe I might have a chance to stay, so I’m filling out an application right now. But I’m really unsure how to address the two years spent at my previous school.

I mean first off, I have no grades, because my condition was so bad I’d have panic attacks even trying to leave my room during exam periods. And then, the uni did ask me to leave since I just wasn’t capable of being a good student. Do I admit I’ve been “sick”? Or do I leave it blank (though that doesn’t sound like a good idea)? And is there a way to prove I’m well enough to be in class? I just don’t know how to address it at all. Other than this thing I meet the grade requirements, and I think I have a strong application.

I know it’s such a long shot, but I just can’t miss this opportunity. I want nothing more than my life back, and being in academics again is SO important to me, but I can’t believe I have such little time. Any advice is appreciated more than you can believe.