What the Hell is wrong with me?

I have never been one to ask for help before. I have always been happy with my life and I have lots of friends. I am currents 16 (male) becoming a senior in high school. I take 7 AP classes and involved in three varsity sports. I’m working as a lifeguard this summer and volunteering at the hospital. The girl is like is a sophomore who is my neighbor. I felt a physical attraction towards her but as I got to know her I could help to “love” her. One day I came out to tell her how I felt she felt flattered but said she didn’t feel the same. I was fine with this I didn’t really feel anything. As time passed she “fell in love” with a dick of a guy. He is currently making out with her one minute and another girl the next. SHE IS FINE WITH THIS. They are fighting over this guy. This left me to feel only hatred for her. I ignored her for a whole 2 months, she didn’t even try to get in touch with me at all. For some reason tonight when I thought of her all I could do was cry. I never cry I have never get emotional. I feel like a wierd stalker who is a freak... ALL I WANT IS TO GET OVER HER! WHY CAN’T I? I have been currently dating a sweet girl but it all feels hollow to me! I feel like a dick every time I take her on a date. WHY CANT I GET OVER HER? WHAT THE HELL IS WRONG WITH ME. WHY IS THIS HAPPING?