<human>: A few years ago, I had the pleasure to meet a cute girl at work. We hit it off instantly (a rare occurrence for me) and after a week or so of talking, I developed a crush on her. 

What I didn't expect at the time was that crush turning into straight-up love. We've known each other for going on 4 years now. In that time, I've realized that she's everything I want in a partner. She's my best friend and she means absolutely everything to me. I'd honestly marry her today, if I could.

The big problem is that she has a boyfriend, who has been with her since a few months she and I met. They've had their share of problems, but for the most part, they're still going fairly strong and I don't see them breaking up anytime soon. 

I'm at my wit's end about what to do about controlling my emotions. At any given time, I'm trying to deal with 5 or 6 conflicting ones. She knows exactly how I feel about her and occasionally we talk about those things to try and help, though I try to limit that as much as I can. I don't want to do anything to come between her and her boyfriend, but it's hard to sit on the sidelines and watch their problems unfold. The only other thing I can think of doing is cutting her out of my life completely, but that just isn't going to happen.

Can you summarize the given text in a few sentences?
<bot>: I'm in love with my best friend who has been in a relationship for 3 years. I've never been good at dealing with these feelings, but now it's becoming almost unbearable. I don't know what to do anymore.