What to do..?(anyone..please?)?

Since a month ore 2 I have a new colleague at work..and from the first moment I saw him I felt a strong attraction towards him.But I soon found out there are several reasons why I shouldn't act on my crush.He's younger than me,we work together..and...he has a girlfriend.So off limits,obviously.

But now it seems like every time I see him,my feelings for him grow stronger...and to make things worse he's giving me all kinds of signals he likes me too(looking at me with this smile on his face-a lót,

''casually'' touching me,taking every chance to be around me..and the other day he told me he was sorry we didn't work together more often,because he likes me.

I know,I know..no good can come of this,he has a girlfriend,I shouldn't even bother,but this situation is driving me nuts!I'm confused,cant stop thinking about him,can't concentrate on my work when I'm arround him,I'm afraid that people at work will notice somthing's up,that I can't hide how I feel much longer...I don't know how to handle this anymore!What would you do?Please help,I'm going insane here!