It's sounds like you are initiating connecting with the guy as much is he is with you, so are you trying to make your boyfriend jealous when he is handeling this like a mature adult? A mature adult don't get jealous of someone they trust.

But if I was you, I would start limiting contact with the guy because you are basically starting to emotionally cheat to get a reaction from your boyfriend

I'm not sure how to explain it... He feels like he needs you to survive, he may turn to stalking you to try to "win yoy back".

You have to make it clear to him that what he is doing is unacceptable, and if he cont, get a restraining order

Say it with me.... Ma... Ni.... Pu... La... Tion.... Manipulation.

He may also have a very dependent relationship stile which would make it worse...

If you are "falling for someone else" then you do not love your girlfriend