Welcome. I am so sorry you find yourself here. :(
I think this line from your post says it all:
He put her feelings ahead of mine.
He has put her before you and lied to you time and time again. In your position, gently, I would believe they are still communicating. In your shoes, I would:
1. Start to pull a 180: http://www.survivinginfidelity.com/forums.asp?tid=232785 To protect yourself, your child, your heart, empower yourself, and maybe, just maybe, wake him up. (You cannot "nice" him back into the relationship.)
2. Read through these posts: http://www.survivinginfidelity.com/forums.asp?tid=361740
3. Most importantly, take care of yourself: plenty of water, eat what you can (drink Ensure or Carnation Instant Breakfasts if you have no appetite) -- do something just for you every day, whether that's going to visit friends and family, volunteering, taking a class, getting a massage, etc.
Gently, I think your BF is feeding you a bunch of bullsh*t.
he admitted to the affair saying that he had believed I had moved on away from the relationship and didn't know that I still wanted to be with him. We has extremely bad communication issues in our relationship on my part so I do accept my responsibility. I asked him if he loved her and he said no, that it was all just a game to him and that he wanted to work on our relationship.
This is a bunch of blameshifting and damage control. Of course I could be wrong. However, the more you're on here, the more you'll see there's almost a script circulating out there amongst those who cheat. I know when I first posted here, someone responded saying that there was likely more to the story, and honestly I was a bit defensive/offended, thinking "I know him, YOU don't!!!" However, if I could remember who that responder was, I'd thank her.
My initial post was about a myspace page with one friend, a female, who lived near where my FWH was doing a temporary work gig. Read my profile if you'd like to know how it evolved from there....or should I say, "mushroomed".
Read, read, read, read here on SI. Read in the Healing Library (look in the upper LH quadrant of your screen, it's a link in the yellow rectangle), read in this forum and the General forum. The links given by mysticpenguin are a great place to begin.
A warning, though: at this point I would be shocked if your BF doesn't go underground with his behavior. He now knows how you learned of your information, and he will therefore be likely to become stealthier. It doesn't mean he's stopped. Earnest apologies are not the same as change. You are NOT crazy; one thing you'll learn in a hurry is to trust your gut.
It may or may not be relevant, but I do find myself wondering why you've been together 16 years, have a child, and aren't married? Was that coming from you or from him or from both?
Hang in there, you're not alone with this now.
I read in your post saying you accept your responsibility, and while it's good for us to admit where we may not have been perfect in our relationships please don't for a second blame yourself for any of this. This was HIS decision and his decision only. Take care of yourself - we are all here to listen when you need someone.
I have seen a lot of BS (myself included) assume too much responsibility. Thinking if they can fix the problems in the relationship then they could have prevented the A.
You can't when dealing with a broken person. Healthy people make better choices when dealing with issues/problems in a M. Broken people cheat.
I can only control myself, no one else. I do not have that kind of power.
Also, should I call him on suspicious behavior? If I think he is doing something right in front of me such as possible texting?
YES! There is nothing worse than blatant disrespect. You need to push back from that type of behavior. Respect yourself by not letting anyone, including the one that is supposed to love and respect you, make a fool of you right in in your face!
I think the disdain WS's show to the BS is criminal!
Familiarity breeds contempt...INDEED!
Never forget what is worth remembering or remember what is best forgotten.
Recognizing and owning your part is good for you.
But he did not cheat because the relationship was bad.
I owned my own part in the M. Then I discovered his earlier online EA. I started to realize my reactions to FWH pulling away due to his cheating was unhealthy, but the dysfunction was largely in part to FWH EA, trolling for a PA and his EA/PA.