Love my b/f but......Then I met this guy.....=(?

Ok. I've had my boyfriend for 3 years. I love him so much and he's my best friend and we plan on moving out in the next year. I never thought I would EVER cheat on him!! But then this guy from work came into the picture. I used to actually hate the guy, couldn't stand him! He would never talk to me and I wouldn't talk to him and i was fine with that....but then about 5 days ago he just came out of no where and started messing with me and stuff you know. I felt so horrible when I realized I started having some feelings for him. There were so many other guys better for me at work and that wanted me but no one ever made me want to be with someone else but my boyfriend...and then he comes along. He's starting to hang around me more even when he gets off work. He just pops up out of no where and is just there around me. I'm afraid if he makes a move I wont stop him!!! Idk what to do....I'm not even sure if he likes me!!! My friend from work is suspicious though because of what him and one of his friends said...so idk. Hu what is wrong with me!!!???? I can't believe this. Everything is great between my boyfriend and I but then this stupid guy is ruining it and I can't stop thinking about him and being with this guy!!! I don't want this! I want him to go away and never return...why is this happening! I know I want to be with my boyfriend so why am I wanting to be with another guy that I know would be so hard to get in the first place!?