Who is this person?

[Day by Day]

Thanks Esox,

Hmmm... well, that's what our big fight was about. I am jealous of his running partner. A blond, cute twenty-something who he says is engaged. Here's the story that I didn't start off with:
Back in Jan. I met him at the finish of a marathon and he was desperate asking where is A? It put me off that he was so concerned for her. He said he just wanted to know how she did since they were running together. Then in March there was a corporate 5k and I met her. Very friendly has lots of friends. She was asking me if I was going with my H to the Marine Corp marathon... I thought stupid question, of course I would, I support him in all his marathons. This got me bothered and I told him I didn't like him running with her. At this time he joined FB and started adding lots of single women from his running group and said not many men he knows have FB. (BS)

In May before our fight I told him I'm very bothered about him running with a single woman and it's inappropriate. I saw on his FB that she said she'd met him in 5 after work which was new because he always ran in mornings before work. I got furious with him because he hid it from me... bad sign!! He said there's nothing going on and she's engaged. She has a photo of her BF on her profile. But his profile has the same photo. I know, Cheaters LIE. Well, I blew up and lost it. The fight was ugly. I posted on his FB that I hope he won't be running on Mother's Day to spend it with me and that p*ssed him off. He took me off as a friend and deleted my comment. The next day he moved out to my SIL's house and has been there ever since.

He denies and swears to his mother and grandmother there is no OW and is offended (holy cow) that I doubt him. He is deeply offended the kids heard us fighting and he is humiliated. Ugh. I haven't proved there's OW, but the signs are there to me and incredibly he keeps denying it. I found on FB pictures of the weekend of the blow up of him with a different blond hugging her. He apologized and said it was inappropriate behavior. He was flirty and trying to get the attention of other women before this all happened and I called him on it. He said he said he just liked to see if he still "had it". Another bad sign.

I don't know if now almost 5 months later if there is now a OW. Don't feel like finding out. He says he's too busy with his own life to have anyone in it.

So guess I needed to get out this other info on my situation. I'm pretty disgusted with it all. I hate this flirty man he's turned into and doesn't think he's playing with fire running with single women. I was and still am bothered by his attachment to his running partner.

Don't know what to do about this.