@hussshy,
Of course you can break up with him. Here's your script.
"I'm sorry, but it's not working out between us. I wish you all the best."
Then go, and block him on all forms of social media.
Boom! Done.
And then you can screw anyone you like (or, apparently, don't like).
Really, it's not hard.
I realize you haven't done it before, but your boyfriend (even you refer to him as your ex) will not break into a million tiny little pieces, even if he is hurt. **** happens, but he can recover. Don't be his mercy relationship. It's not fair to any of the four people in your scenario.
Wait? I hear you asking. Four?
Yes. Four.
- You
- The ex/soon-to-be ex
- The gentleman you sleep with but apparently don't have feelings for and
- The person you really do end up with in the end
Seriously. You will look back on this in a year and wonder why this was such a big deal to you, and why it was so hard to cut the ties.
Cut them. You aren't in love. You're just comfortable, and you don't want to face the fact that the relationship failed.
Well, relationships fail all the time. That does not make us bad people.
It makes us human.