Does he make you feel secure? When you bring this up does he just brush it off as "oh stop being so jealous?".
It's not your fault you feel jealous, a whole lot of people are in a similar situation, it helps a whole lot if you can bring it up with your partner if you're ever feeling a bit insecure and they can re-assure you and make it all better.
But I guess if they just snap and say stop being so jealous, there's not really much else you can do!
It's not fair to stop him speaking to his friends, you either trust him or you don't, but everyone who loves someone goes through those "urgh why do they love me, they're going to go off with someone else, they're doing it right now!" periods, you just need to be able to talk to each other about it, try speaking to him about it without getting worked up.
Just explain that you feel a bit jealous, yes, but you know he loves you and would just like a bit of assurance.