Hey gents,
another problem from here.
This is the situation (it's long, but try to keep up mates

):
1) [Some background story]:
I'm in a LTR right now, on the fourth month.
It's really serious, and we have a really balanced relationship -
with me as the Alpha.
When we were flirting, she suddenly slept with a guy
- and I cutted the contact to her: In 5 months(!).
Then I called her, and we gave it another chance
- now we are in the LTR.
2) [So, here is the roles]:
The ex-lover:
He is dissing my GF alot
(telling people alot of lies about her and so on,
without her knowing it - how I know: a friend),
and he have alot of attitude,
but in a very complicated way
(you never know when he is ironic or real),
so it attracts many girls - and also my girlfriend at that time..
What I've been doing:
I've told my GF that I have a really big problem with this guy,
and I have thought about kicking his ass
(she is responding very respectful about me saying that).
I've also told her, that I trust her,
and I know that all he is saying is lies about her!
My GF:
She have been attracted to the ex-lover, but when she slept with him,
it was because she missed me (I was at a boardingschool that time,
so I was not home very often).
She were crying all the time we had cutted the contact.
Now she is very very happy to be together with me,
but she hates when I bring up the subject about the ex-lover.
She says that it is past time, and we should not focus on that anymore!
But I can't really ignore it, because of this:
3) [Situation up to problem]:
SO, 3 nights ago he called her and asked
what she was doing.
She was sleeping, so she told him,
and then he said "Okay, goodbye then".
Luckily I was sleeping over, so she woke me up,
and told me that he had called.
I told her that I hated that guy,
and she should find out why he was calling her.
My first thought when she told me he had called was:
"He is seeing her as a booty-call"
- so I also told her so and she got really pissed at HIM.
Next day she called him and asked
why the fuck he was calling last night,
and he responded with this:
"Hey, I was just in the neighbourhood last night,
and remembered that you were living here,
so I just wanted to take a smoke with you and you'r boyfriend.
You'r still together, right?
He's a nice guy!"
Of course he was lying, we hate each other
(how I know he hates me - a friend. Yeah, I got insiders

)
- but as said, he is very complicated,
so you get confused if he is ironic or real
- and so did my GF!
She hang up on him, and told me all what he said to her.
I responded with "I'm gonna talk with that guy!".
4) [Problem]:
I've talked alot with my GF,
and we have the same meening about him
(both hate him, and think that he just should meddle around our relationship.
She also knows his relationship to me now)
- but still, I think that I have to handle him in front of my GF,
'cause otherwise I'm feeling out-alphaed,
because he can do whatever he wants and still I'm only reacting to my GF.
I have not talked with him yet,
and I've told my GF that I don't wanna have anything to do with him............
Btw.,
bonus-info:
When me and my girl were flirting, I was chilling a bit with the ex-lover,
because we have much of the same friends.
We had a very "Gentlemen-relationship" to each other,
but could also have some fun together.
So he knew what was going on between me and her, before he slept with her.
So guys, any advices?
Cheers, and thanks in forward!