Infidelity Support Group
Any relationship in which one partner engages willfully in sexual relations with another outside of the partnership is considered to have experienced infidelity. This breach of trust is often traumatizing for the faithful partner as well as the relationship, and support is often needed to heal emotionally and to decide whether or not the relationship should continue after...
I would ask first if either of you tried ic(individual counseling) or mc(marriage counseling)? If not then that would be a great start. Remember that the counselor needs to be somebody you are comfortable with.
Second question is , how long have you been married and do you have children?
5 months is not very long. It can take a couple of years to find a place in your marriage where you are happy and learning to trust.
The fact that they work together is adding insult to injury. Is there any way he could request a transfer to a different location or department?
Sending cyber ((((hugs))))
It took me about 2.5 years to get past the urge to punch my CS in the face for being such an idiot. Like everyone above said, it takes awhile to work through this process.
Are you in counseling -- either individual or couples?
One of the best books I've read on the subject is "NOT Just Friends" by Shirley Glass. It really breaks it all down to help you understand why it happened and what it all means.
http://www.amazon.com/NOT-Just-Friends-ebook/dp/B00120955S/ref=sr_1_1_bnp_1_kin?ie=UTF8&qid=1366593625&sr=8-1&keywords=not+just+friends
Hang in there - it gets easier with time!