My ex boyfriend wants to get back together but only on his very specific terms

So my ex boyfriend identifies as poly. I don't. He said we could be together if we opened up the relationship but I would like to do couples therapy so our relationship can feel more secure & stable before opening it up since I am insecure. He just let me know he would "flip out" if I had another male partner. He says he wouldn't be able to handle it. So he doesn't think this would work. Am I doing something wrong?

You are not doing something wrong. You say he’s your ex-boyfriend and my advice to you is to keep things that way!

For one, exes are generally exes for a reason. For another, he’s told you that he will only get back together with you under certain relationship conditions that don’t align with your identity and make you feel insecure. For a third, he’s trying to establish a “one penis policy” (or “one dick rule”), and those are gross and bad for everyone involved. For a fourth, he’s already threatened to “flip out” and said “wouldn’t be able to handle” an open relationship where you can date as freely as he can.

Let me repeat: YOU ARE NOT DOING ANYTHING WRONG. This guy is trying to manipulate you by making you think you’re somehow in the wrong for not wanting to be in a relationship with him. Even though he has explicitly admitted that he “doesn’t think this would work.” He is not entitled to a relationship with you, under his own terms or under any terms! You are not obligated to try and twist yourself into a concession pretzel so he can get what he wants from you! Leave him firmly in the “ex” category, lose his number, and find someone who can actually have a healthy, fulfilling relationship with you.