Over a period (close to a year) I've fallen in love with one of my coworkers.
She's bi, in a relationship with another woman,I'm a guy in a relationship of a lot of years with a woman.
I haven't told any one this,well because. We flirt @ work and talk about some deep and personal things.
I could so easily make a big mess of this,well for me it already feels like one. She's always in my thoughts.

Aaaarrrrrggggghhhhh I don't think there's really a question in here but oh crap.

You're in a relationship so is she. Stop playing with fire and tone down the conversation.

I would hold your horses.

First of all, she's got to partner.

Second, this is all at work.

That's 2 strikes in my book.

The third is you don't really know what it is you want. Or who you are.

Figure that out first. Counseling? Could be just the ticket.

"a big mess of this,well for me it already feels like one"

Go with your gut.