Going CRAZY over a co-worker... how do I let go?

I have developed feelings for a co-worker. The feelings are the result of hours of intense conversation, (unusually emotional conversations, for co-workers) countless invitaions to his house, invitations to family dinners, to spend our lunch hours together, etc. Initially the "connection" between us, I assumed, was mutual. Over time, though, I realized that if I didn't call him, we wouldn't talk. 98% of my texts got responses, but I never got any impromptu texts from him. I decided that perhaps I was reading too much into our "connection" and backed away a little. Which he noticed, and questioned... during a conversation that I instigated.

Most recently, I've noticed that he spends a lot of time with ANOTHER coworker of our who, as it happens, was also spending lunch hours with him. The way they look at each other appears, to me, to be loaded with sexual tension. They speak OFTEN, off the clock via phone, and have a few things in common. They flirt ALL the time. He's mentioned their relationship to me in the past, and says it's genuine but lacks substance... and that I am one of the few he can talk to about ANYTHING. He downplays their relationship when I ask him about it... but what i SEE between them says otherwise. I know that we are not together, have never had sex, or even communicated a mutual sexual attraction (verbally). On one hand I feel like I'm being played. On the other hand I kick myself that I allowed myself to develop feelings for this guy with know concrete evidence that he's even interested in me. Either way, I'm fnding it nearly impossible to b around this guy, and my stomach hurts when I see the two of them together... so I avoid them both... completely. Have I completely over analyzed this situation and his relationship with this other co-worker. Or do you think I've judged the situation correctly, and should move on completely... IF SO... HOW do I do that having to be around them both... daily? HELP ME!!