See...that is what happens when u play around too much....
But what is past is past...

I am sure that ur current gf is suffering quite as much as to trust u or not...
Better hope she dont leave u for a better guy though...

Best thing to do is cut all contact with that Joana girl...
Change ur hp number, delete her from ur FB etc...
Get a couples number with ur current gf...

Like u said, u have a lot of feelings for ur gf so put in some effort....
Once u tried ur best ask ur gf to trust u...

If u've really changed and ur gf still don't trust u, then it's her prob already...
Means she nit enough confident....