Q: I met my ex at work. We lived together for three years. We had no children while we were together and because neither one of us wanted to quit when we broke up, we continue to work together. I have to speak to him on occasion, and it wasn't awkward until I met this new guy at work that I would like to date. Do I have to tell the new guy that I lived with my ex for three years? What's good ex-etiquette?
A: The big red flag in your question is that you date guys at work. I don't know what the rules are at the company at which you work, but if you want to be taken seriously, find another place to tap into the dating pool. Whether it was a good breakup or bad, people will talk. I'd be surprised if the new guy doesn't already know that you used to live with your ex. We are talking great gossip around the water cooler.
If dating is permitted at your company, date someone who has nothing to do with your work position. In other words, don't date or sleep with your boss or subordinate. It puts both of you in an awkward position for which you could be fired.
Don't communicate using the company e-mail system. It's most likely not permitted and again possibly a reason for termination.
No displays of affection at work. Very unprofessional. Wait until you get home.
Finally, if you really think this might be the love of your life, consider leaving your job before you start a relationship. If it's just a fling you're after, don't do it at work.
The biggest objection people seem to have to dating a co-worker is the inevitable discomfort of going to work after the breakup, which is reinforced by your original question — do you have to tell a new guy about your ex? The answer is no, unless you feel the info might help the new person to better understand you.
For example, if your ex was violent and you suffer with post-traumatic stress disorder as a result, or your ex was unfaithful and you have trust issues. Offering that sort of information is certainly understandable, but talking about your sexual history is very bad ex-etiquette. The new person in your life doesn't have to know how many people you've slept with or the intimate details of your encounters. Volunteering that sort of information is bound to backfire. It promotes insecurity and jealousy and is not conducive to building trust. Just bad ex-etiquette all around.
Truth is, if you lived with your ex for three years and continued to work at the same company, it's doubtful it is a secret. Your new crush probably knows all about it. If you do choose to go forward and date yet another guy from work, your best bet is have a breakup contingency plan in place before you even start. That means decide how you will handle your breakup while at work should you decide to part somewhere down the road, and respect each other enough to stick to it.