How ti stop my GF from getting an abortion?

I'm not sure you have any legal rights but I would talk to an attorney who specializes in family law. If she has an abortion out of spite, she will regret it later on. Have you thought that maybe she doesn't want to keep the baby because it isn't yours? If you were told you were going to have to adopt because of your extremely low sperm count, then I would wonder if she has been totally faithful. Just a thought. All it takes is one sperm, but I wonder what the real reason is for wanting an abortion.