My girlfriend left me for a rich man. She's pregnant!

So long story short, my girlfriend of a few years leaves me for a man who makes alot more than I do. I treated her very well for a man of my income.

I just seen her yesterday for the first time in 3 months and she's sporting a pregnant belly!

Is that my kid? She wouldn't be showing so soon if it weren't right?

I want to confront her and him, but at the same time. Am I an asshole for possibly ruining a better life for my child, if it is mine. Or do I need to mind my buisness it's his baby?

Edit: I work for a supermarket chain. He is a lawyer.

Edit #2 there was no warning, I woke up and she was gone. I got a text saying it was time to move on , she had "outgrown me" , I washed my hands of her. I didn't need her if she didn't need me. Then THIS!

Edit 3 : her belly wasn't just a noticeable little pouch. It was like Bam! But I'm a dude, and could be totally assing this up.