So nice you decided to have a blog! It's giving me a lot of food for thought already.
1) The military thing. Do you feel that him being away from home for long periods of time (?) created distance between the two of you, or did it just take the attention away from the distance that was already there to begin with? Do you think you would have been able to re-connect if he had been involved with someone else at the time? Was he?
2) There are a lot of assumptions going on in the therapy business on how non-monogamy is ultimately destructive for a relationship, sometimes together with covert homophobia. The most recent example I can think of was a story of a happily monogamous woman who unexpectedly fell in love with an older woman, and after six years (!) called things off (the hubs was aware of the situation the whole time). Instead of focusing on the intense re-evaluation this woman was going through for the whole of six years (impressive length for a first non-monogamous AND same-sex relationship, methinks), the writer of the book explained how this 'need' to have a relationship with an older woman was a result of insecure attachment to her mother in her early childhood. Of course, because she just couldn't be a bisexual or lesbian, much less honestly being happy with her husband while still wanting another relationship with someone else - there had to be something pathological behind such non-monogamous choices
3) I have a diagnosis for GAD, which I no longer fully identify with, but it certainly helped me to understand how my sympathetic nervous system was just wired to go off from stimulation that others wouldn't probably pay any mind to (I am easily distracted and have trouble prioritizing stimuli). I hope you get some answers from your visit to the therapist!