Jealous boyfriend?

The guy I’m seeing says he cares a lot about me. He’s either sulking or getting aggressive whenever I have any contact with men (regarding school or work). He’s been acting increasingly more jealous and controlling lately for no reason. I’m at a loss as to why because I sure never gave him reason to be. I love him. Is it all due to some sort of insecurity on his part? Anything I can do to make him feel less insecure?
Jealous boyfriend?
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