Relationships

Am I overthinking this or is this worth a break up?

Me (F21) and my boyfriend (M33 ) have been dating for 2 years. He broke up with his ex girlfriend of 6 years, 3 years ago. They fell out of love and decided that being just friends is better, so they broke up. Since the break up they continued to stay close friends, which I am not very comfortable with. Therefore I created some boundaries such as: no facetiming, no going out one on one, and no going over to her house or definitely ever sleeping there. All these things he used to do when we just started dating and after a few months I asked him to stop. He agreed even though was a bit unhappy about it. Last year he told me that he wants to call her (not FaceTime) on her birthday because they haven't been talking for weeks and it would be nice to catch up. He also said that he felt guilty for barely talking to her without giving her an explanation. I agreed. However, he never calls any of his other close friends for their birthday so seeing her get special treatment bothers me. Her birthday this year is coming up next month and he insists that he must call her again. Saying it is just one time a year when he calls her and I should not be so controlling. But I don't see why he needs to do it. He doesn't do it with any of his other friends (a text is enough), he knows it makes me uncomfortable, and he already explained to her why they don't talk as much as they used to. It has been 3 years since their break up and he has been in a committed relationship for 2 years. But he still chooses to make her happy by calling, knowing how much it bothers me. Should I just let him do it and forget about it? Or is he still too attached to her?
Am I overthinking this or is this worth a break up?
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