I'm going to leave my boyfriend and sleep with my fuckfriend the next day
Why in the world would you do that?
I don't like sex very much with my boyfriend.
I guess you know what you want. It's probably best to wait a bit after you break up with your boyfriend to have sex with someone else.
I don't care if we break up, I'm not loyal to my boyfriend.
I know you are not loyal but you need to do the breaking up before you hurt your boyfriend more. It would also be good for you to wait a while before your next relationship so that you can think about what you want from them and what you can do for them.