Can I use "break out" instead of "break up" when I split from boy/girlfriend?
No, I don't recommend using that. Native speakers will be very confused if you say this." You need to the phrasal verb "break up" to indicate that you don't want to be in a relationship anymore. Ex: I don't think we are working out. I want to break up. Ex: I'm breaking up with you. I can't trust you anymore.