Huge crush on a guy at work but boyfriend at home!

I have been with my live-in boyfriend now for 5 years. We have been living together for about 2 years. Starting 2 months ago, this new guy started working at my job. I was instantly attracted to him and it's gotten stronger each day. Right around the time this crush was forming, I started questioning my relationship with my boyfriend, because I never felt this way about him when we first met and I feel like we are more friends than lovers since we have been together so long. Well the sex isn't good at all and I never want it.
Anyway, I found out that my crush has a girlfriend who he's been with for 3 years. The thing is, she is going away for 3 months and apparently isn't moving back in with him when she comes back or he isn't sure. In the beginning I thought maybe he returned my feelings but now I'm not sure if he's just being a nice guy...I.e. flirting with me and such. He picks on me a lot...and when we go out after work he stays with me until everyone else leaves and walks me partially home. It's very hard because I do love my boyfriend but I am so physically attracted to this other guy that I can hardly stop thinking about him. I don't want to hurt my boyfriend, he's my best friend...but sometimes I think I would risk it all for this other guy. What should I do. I don't even know if this other guy feels the same way.

I would avoid your co-worker and work on your current relationship. You don't want to throw a 5 year relationship down the drain and if the sex isn't good - MAKE IT BETTER! Communicate with your boyfriend!

I THINK YOU SHOULD AVOID THE CO-WORKER ASWELL.... THE SAME THING HAPPENED TO ME, I'VE BEEN WITH MY BOYFRIEND FOR 1 YEAR AND HE IS THE BEST THING THAT HAS EVER HAPPENED TO ME. AT THE SAME TIME, I HAS A CRUSH ON THE "NEW GUY", TILL I FINALLY SNAPPED OUTTA OF IT. YOU AND YOUR BOYFRIEND MAY HAVE LOTS OF PROBLEMS BUT LET'S SAY YOU DIDN'T want to WORK IT OUT BECAUSE YOU THOUGHT THIS OTHER GUY WAS going to MAKE YOU HAPPIER. COME TO FIND OUT THAT YOU ENDED IT WITH YOUR MAN, STARTED DEALING WITH THE OTHER ONE AND AS SOON AS HE GOT A PIECE OF YOU HE LEFT YOU, TELLING YOU THAT HE IS STILL IN LOVE WITH HIS EX. DECIDES TO BRAKE IT OFF WITH OU AND THEN WHAT????? YOU LOST YOUR MAN, YOU LOST THE OTHER, YOU WILL NO LONGER BE FRIENDS AND WHAT NOW???? FEEL STUPID DONT YOU??? SO YEAH.... BACK TO MY SITUATION... I LOVE MY BOYFRIEND MORE THEN ANYTHING.... EVEN DO WE ARE LIKE CATS AND DOGS.... BUT LET ME TELL YOU THAT THE SEX IS GREAT!!!!!! SO IF YOU HAVE ANY PROBLEMS WITH YOU SEX LIFE.... TALK ABOUT IT, DONT LET IT DRAG. ANYWAYS, THE OTHER GUY THAT WORKS WITH ME STILLS ASKS ME TO GO OUT WITH HIM AND FLIRTS, BUT DEEP DOWN I KNOW THAT MY BOYFRIEND IS THE ONE!!!!! HOPE I WAS A BIT OF HELP!!!