Men really are like buses

The sequence of events is all a bit fuzzy now.   But the key points in the story are still there.
I called him (to ask if he wanted to do something?) He was having drinks after work with some of our colleaugues, but he went outside to talk to me.
"Yeah, I was just talking to X, and I was telling him about you and I, and he said,... well he said I should tell you that I'm still seeing my Ex.  Cause it's not really fair is it? On you. So maybe we should..."
"Call it a day?"
Later on, I cried my eyes out.  In hindsight this was probably because this reminded me of several relationships I had been in before.
I went upstairs to the laptop, and opened my blog.
And there it was.  Two messages, one of them really long, left on my comments, from this guy.
I promised him I wouldn't publish them , so I won't. 
To paraphrase: he said he missed me, he had finished with his girlfriend and he wanted to meet up (that sounds pretty cold, it wasn't like that, it was actually really sweet, however I'm sticking to my word).
This was a shock.
After all I hadn't heard anything from him for Two years! Not a text, not a facebook friend request- nothing!
But that is a divergent story. 
I went out of my way to persuade the Guy I Ended Up Having a Relationship With to change his mind.  The result was, that I ended up seeing them both. I figured if we're both seeing other people then we're quits. 
Maybe some of you readers could enlighten me on this, but How do people do that shit? I mean those people who two -time professionally, or as a hobby or whatever.
It was really weird.  Apart from the logistics for a single parent getting TWO babysitters on a weekend, and the expense!  It got to the point really quickly where I couldn't remember to whom I had said what.
The two-timing culminated one night when I realised I felt really angry with the guy.  I mean, although we were having a fun time dating, two years ago, he chose his crappy girlfriend over Me! Typically unable to voice my feelings, I ran away.  I ran away at the end of one of our dates. It was freezing cold, it was late, and I was upset, so I rang TGEUHRW,  He said, "Yeah, come over.  Bring sexy underwear and fags."