No! -- you can't press charges against him and you can't have him arrested because he ejaculated inside you - not after you agreed to have sex with him.
If you're old enough to be having sex with a male, then you're old enough to realize that it's his natural, inborn (over 100's of 1000's of years), to ejaculate inside a female - in order to continue the preservation the species. He can no more resist that urge than he can stop breathiing.
If you don't want to run the risk of getting pregnant, then you have two options: (1) Don't ever have sex with a male; or (2) Use some sort of birth control yourself, BEFORE you begin having sex with him.
if this guy is your "ex" and he's been verbally and physically abusive to you in the past, then WHY are you having sex with him now?