Failed in past, should I continue trying?

(I'll try to keep this as short as possible, though honestly I could go on for hours)

When I was in High school I met this girl. She was kind of quiet and nerdy (quite like me), but when I eventually started talking to her I found she was really nice(amoungst other things), and I started getting a crush on her.

As time went on though I found myself struggling with depression for the rest of my highschool career, which inhibited me quite a bit.

I still had feelings for her, but I honestly had nowhere to begin, and certainly not the expectation that she'd be interested in me. She started going out with some other guy and I was busy doing other things, like trying to keep living when my brain was trying to kill me.

So at the end of highschool when I started to get onto of myself and back into the swing of things I noticed her again, though she was still going out with that guy.

So after it ended for her (I did my year 12 over 2 years because of the mental issues involved with the particular problem that caused my depression) she dumped him, I thought I could at least give it a try.

Though I wasn't exactly successful, I spent a year trying cautiously to see if she had any feelings back. It was like asking how a brick wall felt about cotton. For about half a year I tried my best to forget my feelings for her, but clearly that didn't work either.

So I decided to bite the bullet one day, went around to her place and told her I had feelings for her, though not expecting to be accepted. Frankly I just wanted to stop thinking about her.

No suprise, she said no. She was fine with it though (one of the things that I love about her), no friendships damaged.

So, after a year and a half of uni, drug and surgical treatments, I'm feeling terrific and awesome. No more depression, no more memory problems, nothing.
Though much to my dismay I still have feelings for her, but I think I might have a chance with her as I am now.

So pretty much the situation as it is now:
-I'm going after a girl who has already said no to me, though I was quite a different person back then.
-Sometimes even the suggestion (not literal of course) of flirting makes her shut down, sometimes she's very warm towards me. Basically I can't really get a clear idea of the general flow of things.
-I'm still not quite done recovering from my illness which can lead to periods where I get many symptoms (of recovery and the past illness), so I'm on pretty shaky personality ground at the moment.

I can't help but feel she's worth going after but with past failings I don't know if I should risk putting the fallout on either of us again.

Honestly I only half wrote this to get advice or thoughts, I also needed to get this out of my system. Who knows, maybe writing all this down will help me decide for myself.

So, feel free to comment etc.