someone needing advice: You are right about people getting hurt if this comes out. One thing you should and your co-worker should ask yourselves is whether or not you still love your spouses. Remember, it is always the kids who get hurt the most in a situation like this (I've already been through this as a kid, mom found someone and described it as "unwise" and my parents later divorced). It makes me wonder how things are going in his marriage. If he cheated on her with, he would probably cheat on you, too. Unless you both are okay with the hurt, stress, drama and financial woes you would be causing, my advice is to put an end to whatever is going on and just be typical co-workers.
Lara -
no one has cheated on anyone unless you mean emotionally. We both find ourselves in love with each other. We want to take it further but do not want to hurt everyone around us. So the question is.. do we suppress our deep feelings for each other and live in our mediocre lives or or do we pursue what could be great love. There is hurt and risk in both ways and so it seems as though no one wins in any situation... :(
I have been on the receiving end of this, and in the end the "great love" my husband thought he had ended in less than a year once life's responsibilities and stresses came in to play. He now lives with serious regrets because I wouldn't take him back.
My advice to you is to take this coworker out of the equation completely for now because you can't make any objective decisions about your future with him waiting in the wings. Seek some personal counselling (and possibly marriage counselling) to see if your issues with your marriage can be resolved and do some soul searching to figure out if you are still in love with your husband.
If you still don't want to be in the marriage then end it, not because of another man but because you don't want to be married to your husband any longer. Make a clean break from your current marriage and take some time for yourself before making any commitments to another man. If you are meant to be with this other man, it will all work out for the two of you in the end, no matter how long it takes.
On a final note, whether you realize it or not, you are already having an affair. An emotional affair is just as serious and damaging as a physical affair.