There are certain things you don't need to share with your girl/boyfriend. Especially you should keep private intimate details of your past life .
I know, sometimes temptation to tell about our ex-partner is huge, we want to discuss some situations that took place during your being together. But it's wrong! You may hurt your girl/boyfriend by this.

I had a guy who was a rather flirty type of person, so-called Lovelace. I realized it, so didn't want to take him seriously, but failed to - I warmed up to him... You cannot imagine how much irritation he aroused in me at times, telling about his past victories over girls' heart. He realized what a hunk he was and was proud of women's attention to his person! I think he got real kicks remembering all signs of attention to him.
No doubt, I couldn't stand it for a long time, I was really fed up with all this stuff and dumped him eventually.

So, after such experience, I want to give you my simple, but nice idea - guys, don't