>After confessing my feelings for her, she hooked up a colleage the very next day

Come on...

I know you weren't dating but "Oh you let me know you had feelings for me? That's cool, lemme just go fuck this guy a minute then I'll get back to you" speaks fucking volumes to how little respect and thought she gave your "confession of feelings"

Never mind the rest of this dumpsterfire. History of cheating aswell? Come on man... just walk before you end up sinking more time into this.