sunflowergirl - I SO understand this!! I've been with my boyfriend for 10 years, things are great! I love him 100%. And then this guy at work, he's cute, we hang out together at work a bit, and I've developed a little crush on him. And he flirts back. He has a girlfriend, and he's friends with my boyfriend (who also happens to be his boss). The part about feeling something you haven't felt in a long time, it makes perfect sense. The "newness" of a crush is a great feeling, makes you remember the first kiss, the first holding of hands (if you are cheesy like me)... I am not going to have those things.. BUT! A long term relationship brings so much better things, comfort, great intimacy - that you can only get when you really love someone. Enjoy the crush, don't feel bad, just don't act on it. I also do NOT share this with my boyfriend, why? Not because he'll get mad, but he might.. I don't tell him because I wouldn't want to him to tell me if he had a crush on someone!
Anyways, long-winded.. hope you get some peace with this
-Aimee