Let me start off by saying that I understand that everybody has their insecurities. The fact that you are uncomfortable/jealous about your boyfriend’s friendship with me doesn’t make you a bad person. If anything, it makes it obvious that you really care about a very dear friend of mine. It’s clear that you’re afraid to lose him; and I respect that.
That being said, I hope you know that I am not your enemy. I'm not even your competition. I do not exist to cause issues between the two of you. I’m definitely not out ruin your relationship. I can tell that he really likes being with you, I can see that you make him happy. Why would I get in the way of that, assuming I even could? Why would I want to mess that up?
Let's be real. If he didn't want to be with you, he would have left already. And he hasn't, which should speak volumes.
I understand why you question the innocence of my intentions when I ask him if he wants to hang out, especially considering the fact that we have a bit of a past (if you can even call something happening once a "past"). However, I wish you would realize that the past is exactly that. I have no interest or intention of repeating any of it. We decided a very long time ago that we were better off as friends. That should have been obvious when he started dating you, and even more obvious when I started dating someone else.
Being jealous does not give you the right to control who someone talks to or hangs out with. If you don't trust the person you're with, you shouldn't even be with them to begin with (and don't even say that it's just because you don't trust me - deep down, it's a trust issue with him as well). If you have insecurities that makes you controlling, maybe you need some time by yourself to work those things out.
I'm not trying to come across in a negative way. Everyone gets jealous; it's human nature. However, it's not healthy or right for you to control someone you care about. I understand that you don't want to lose him; I don't want to lose him, either. He's one of my best friends and he's seen me through a lot.
I'm definitely not asking you to walk away so I can have him all to myself. I just want my friend. That's all. And maybe, just maybe, you and I could end up being friends as well.
Please consider it.