I don't know about some of you wanks, but if I was datin' a chick and then all of a sudden "BAM!" I found out she had, or was still involved with her ex-boyfriend's kid. I'd take slowly take 5 steps back, turn around and jet.
Of course you would, and I wouldn't blame you.
Relax... I'll need some information first. Just the basic facts - can you show me where it hurts?
Dude, what did you think was going to happen when you brought her home? You just didn't have the balls to broach the subject ahead of time and presented her with this tableau that had nothing to do with the person you were purporting yourself to be- YEAH it was a lie of omission, YEAH you ****ed up, and MAYBE she'll give you another chance.
IMO- it wasn't the fact that you have this kid in your life that was disturbing, it was the fact that you didn't see fit to mention it at all. That's what I would need time to think about.