It’s basic human nature to be jealous. And if it’s someone you love more than life itself, of course you’ll be jealous. I’d be surprised if you weren’t.
But never doubt.
You can’t really cut off ties with everyone, once you’re in a relationship. Nor can you ask the other person to break them off, just because you don’t like a certain person, or you’re jealous of him talking to another girl.
So he’s talking to the girl in his chem class. She helped him with his assignments, something you couldn’t help him with.
His neighbour bathed his wounds one day when he was alone and hurt himself. She was there, and of course he couldn’t ask you to drive over and not try to stop the bleeding.
He talked to his ex the other day. They parted amicably, and continued to be friends. She’s seen him at a bad time, and he can’t forget how she helped him.
See? You can hope and wish that he didn’t talk to all these girls, but a point had to come where you realise you’re his present and his future. He may talk to them, but you’re the one who has his heart. Have faith in his love.
Look at it this way. He’s not the only guy you talk to, is he? Guys in your class. Your neighbours. People you’ve known since childhood.
While you’re talking to them, you don’t forget how much you love him, do you? You don’t lose sight of what he means to you. Of course you won’t be leaving him and falling for whoever you’re talking to.
Then why do you think he’ll forget what you mean to him?