@claudia85,
Wow, the nighttime folks didn't pull any punches, did they?
Chances are the two of you will not make it long term. I agree with engineer. There's a reason you ended up having an affair and it probably stems from your marriage becoming mundane and boring with all of your "couple" energies taken up by the demands of a baby.
I didn't see that you blamed your husband in any way, nor do I think you're foolish, stupid, or a hussy. I think you're in a situation that is extremely complicated, particularly since you and your lover are co-workers.
My suggestion is to start talking to your husband. Figure out what it was that brought the two of you together in the first place and see if you can put some energies into those very same things. You're finding the time to be with another man. Find the time to be with the one you're married to. Get a baby-sitter. Go out on a date. Spend time in the park together --- anything that gets you out of the house for a bit and puts the two (sometimes three) of you together.
If it turns out that your marriage is hopeless then take the proper steps to terminate the marriage (hopefully with full joint custody of your daughter). In the meantime, I'd strongly advise against a relationship that could in any way jeopardize your job. My advice is to nix the affair. You're burning both ends and the middle of the candle all at the same time. Give yourself some time to get some perspective on your marriage. Your lover has been married for 17 years. He's not going anywhere any time soon.