Why do I have to make things so complicated for myself?

Right now I'm a bit disorginized in my thoughtpattern but I'll try to explain everything as good as I can.

I recently started studying again after taking a 4 year break and started hanging around in a IRC-channel for the school. There was this one really cool dude that I talked to alot. He reccomended that I'd join a mentoring program the school had and I did.

The first meeting I meet this person and it's a girl. Not only that but she's attractive. I start snooping around and find out she's engaged, so I just decides to admire her from a distance. Over time my feelings for her started to grow and we could talk for hours. She's smart, good looking and we agree on so much. Now last week I found out that she talks about me alot and that she'll find any exuse to be with me (let's forget that she's engaged, that's a completely diffrent conversation). I denied it at first but some common friends "convinced" me.

After I was conviced that she liked me aswell I've just been feeling so depressed. I want to be around her all the time but for some reason I get jealous when I'm not around her but a friend, who has clearly stated he is not interested at all, is. I've been trying to talk myself down, like I've done plenty of times before, but this time something is different. Yesterday we were all hanging out. I was on one couch semi-sleeping and she was on a bigger couch with my friend. She put her feet up in his lap, nothing weird with that really, but I just felt how everything started to spin. I exused myself and said I had to leave because I was "tired".

Walking trough a hallway on my way home I just felt like sitting down in the corner and cry. I kept on walking, when I got home I was still really overwhelmed. I tried to get myself to cry by listening to some really sad music but I couldn't. I slept for 3 hours and still felt really depressed when I woke up. I go and sit down by the computer and start the music again. And then it all just hits me in the face. I cried and cried. I haven't cried that much in years. I just sat there with coldplay in my headphones and wept for 30 minutes.

Today has been pretty much the same but without the "stresser". I basically avoided her all day (but I just can't stay away so I still met her). I got home, waited to start crying, trying to provoke the tears out of me, but it didnt help. I've just slept for 3 hours and right now I'm just waiting for the tears.

I'm really lost here and I don't know what to do. I don't want to break off my contact with her, she's one of the greatest persons I've ever met and earlier she has turned days around for me. Just making her smile gets me really happy.

I just had to get this off my chest, and I didn't feel like it was "bad" enough for r/depression