I filed on grounds of unreasonable behaviour as I didn't have legal proof of ex's affair (I was advised you basically need photos 'in the act' to achieve that if they won't admit it formally) before her pregnancy was apparent.
Even then he wouldn't admit she was further along than he was claiming and the child was conceived while we were still together.
But I put it in the details of the "unreasonable behaviour" -
I can't remember exactly how it was put but something like
Seeking affection outside the marriage in an inappropriate way
And I gave the reasons why I thought this inc suddenly "working late", the texts and emails I'd seen between the 2 of them etc.
All factual, all of which I had proof of so he couldn't legally deny - which he hated!
Because like yours he enjoyed having the reputation of being a "good guy" and wanted to make out it was all my fault.
Of course her pregnancy put paid to that too! Because people didn't believe their bullshit that she was 2-3 months less pregnant than she was.
Yea there's no financial or legal gain but it IS satisfying that he had to sign a form agreeing he'd become a shit husband and father!
And it is true what pp say karma works.
I'm 16 years down the line now. He dragged his heels on the divorce in order to avoid marrying her - which I was able to put her straight on him claiming that was me!
The night before THEIR wedding he was trying to proposition me. He's told me on several occasions completely unprompted by me that he never intended for their relationship to become serious and he deeply regrets us breaking up, the first time he said this was in reaction to that first pregnancy.
He's cheated on her multiple times and I have it on good authority they're both miserable.
They've had 5 kids, he won't leave because he doesn't want to take the financial hit, she won't leave because she fears he'll do to her kids what he did to dd - he hasn't seen her in years and never paid cm reliably.
So I'm really glad I never acted out any of my revenge fantasies because they are miserable PURELY As a result of their own actions and they know that.
Get rid, move on and when karma hits them in the ass laugh!