<human>: I know it's shitty to have feelings for someone already in a relationships, I've already dealt/am dealing with that, I'd like more advice on what to do about it all.

I realised I had feelings for her before the start of the summer break, and I think she had feeling for me too. She came to me in confidence and told me she had feelings for someone other than her bf, but no matter what she'd choose him over the crush. I was crushed, but I kept myself busy and try to fade out of her life, I obviously came second in her life, so I had to concentrate on making myself first in my life.

First week back to uni it was like we were acquaintances, I tried to be cordial, be polite and concentrate on other people...but as the year went on, I became more and more emotionally drained and it became harder and harder to ignore her efforts to rekindle the friendship. 

Now we're practically a couple, she fulfils my emotional needs too, so it's not all one way, but I still feel used, and I am honestly frightened of going back on the emotional roller-coaster I went through during summer. 

Her boyfriend has not been there for her recently, however this is what happened before the summer too, and after the summer before that, and before that summer...she says she feels like she's single...while at the same time, I've been feeling crushing loneliness too, and talking to her does make me happy, she's always there to listen to me when I need someone to talk to, just as I am there for her...

We're in the same uni course, and the same classes, and the same work groups, so no contact is not an option. How do I get through this?

Can you summarize the given text in a few sentences?
<bot>: Classic boy falls in love with female best friend, except there's an emotionally disattached boyfriend in the picture to complicate things. How do I get through this without breaking down myself/the friendship?