Penny -- as you are beginning to understand, the man you THOUGHT you were married to, is not the same as the man you are now married to. Separations are difficult. Separations with situational stress are VERY difficult. Your husband appears to seek escape in others. From what you write, this is his default "make-me-feel-better" mechanism.
My prediction is he is splitting inside. There is his life gone, with OW and the promises he makes to them. And then there is his life with you, home. The two are separated in him while he is away. At home, especially now that you have found out, the separation is not possible.
As is often true in infidelity, the affair partner knows about the marriage and children. But only through a clouded lens as shown by our cheating mates. Affair partners seem to be able to rationalize their actions, no matter who they are, and what the reality of their professional life, or home life is. Take note of General David Petraus, and his affair partner Paula Broadwell.
If you make the decision to stay with your husband, I think you need to decide what YOUR conditions are. If you decide to divorce, be smart.
Either way, I encourage you to follow the good advice of those here who recommended you get a SECURE communication mode and change all your private passwords once you do this. Pay to have someone help you with this, as has been suggested here. It could be critical as you move forward.
My own experience with a cheating spouse who was ex-military, and then working in a career that had him away from home A LOT, was there will be lots of covering, lots of lying, lots and lots of things you never, EVER, imagined possible in your mate. Once they are exposed for the fragile, very imperfect humans they are ... things can get very dicey for you.
BE SMART now.
[This message edited by luv2swim at 6:27 PM, May 27th (Monday)]