Believe me, every kid would rather have divorced parents than an unstable/bitter situation at home. Your relationship with your kid is yours and your kid's only.

And yeah, it's weird that she got pregnant twice knowing your relationship was going through the bumpy road. Were you planning to to have kids before?

I could say something like "consider if it's really a lost case", but I don't really see a point as you didn't mention any hopes or wishes towards it. Sometimes you've got to do what you've got to do, that's how you feel and you can't go on with this anymore.