No it's my wife and ya I am worried no I didn't let it go there was a lot of issues with trust and what not but we started working on it and I thought we where getting better until she made a new friend whom just got divorced and was telling my wife I was possessive of her when I only saw her for a few hours a week do to our work schedule and yes I'd love to save my marriage this woman means the world to me but she's also doing everything she can to push me away
Well, there's your answer to what made her drop a bomb on you last April. She might not have been having an affair at the beginning, if you say that this is a new friend, but she is having one now, and while he's around you stand no chance of reconciling.
I'm a bit unclear about the timeline, but logic would suggest that she had already met him last April, and that's why she dropped the bomb. After you moved out she got her desired freedom to see this man more openly. She probably feels that since you are separated, nobody will see this as an affair and she is free to date. You need to disabuse her of that notion. And if he is recently divorced, there is every chance that this affair was the cause of his divorce.
Do you know his name (don't write it here!)? Is he still a co-worker - meaning that they work for the same organisation? Is one of them in a supervisory position over the other? Does he have kids?
You need to find out as much as you can about his identity, and when you have enough evidence to convince a jury (in Dr Harley's words) you will need to expose this affair to his ex, to both (your and your wife's) families, to your child, and to the workplace.
All of this needs to be done properly and you must not give your game away to anyone until you are ready to expose. Do not start questioning your wife about her man friend, for example, and absolutely do not tell her that you plan to expose at work or to his family. Say nothing at all at this stage to anyone.