Whew...sounds like you need some R&R from all of this!

**usual disclaimer of jmo**
It sounds like there are serious trust issues that need to be addressed by you. Having so little faith in her honesty might be a signal you need to do some soul searching...
She may have to earn your trust back.

Is a legal separation possible? You've got to have some way of protecting yourself while this mess is untangled...well, as much as it can be at this point.

The couples counseling? If both of you are committed to staying together then seek someone who can guide you.
Not her therapist, either.
A therapist who won't be favoring either one of you. Someone like that is more likely to be of help.

Please re the other girl...don't. You have enough on your plate right now without adding this to it. Before you get involved with another woman on any level, you've got to be on level ground within yourself.

I sincerely hope you are also being debriefed before you come home...you are going to have some strong things to work through from being in a war zone. Please don't belittle the affect it has had on you.

My best wishes for you,
Cap