It’s not really about jealousy.
You are very dependent on your relationship with him, and seeing him go to other people means he could lose touch with you and you became worried. Worried that he’ll invest less in you.
There’s nothing wrong with feeling jealous or bad about this, otherwise you wouldn’t be feeling the way you do. That’s my personal opinion.

But with that, I get you. I can be very dependant on relationships and because of that I can end up feeling behind at times.