I'm a former body builder. A guy simply cannot get to be 270lbs of muscle without steroids. She'll have fun with his "roid rage", when he gets extremely angry for no reason from the steroids.
Your gf did you a favor. She removed herself from your life. I hope you can see you can do better. Good luck!
I have a long time interest in psychology, specializing in relationship dynamics for 30 years.
(Please note, we give the best advice we can based on the information given in a post. For better advice, please include the age of all romantic partners.)