What kind of talks your bf is doing about that girl? What do you mean by relatioshionship? Are you got engaged?
New environment and new friends are giving him new good experience. Since you are close to him, he is sharing his experiences with you. If he has some negative thoughts then he may not tell you anything. So don’t be a suspicious girl. Have faith on your friend. If your emotions and love are true and your bf know it then he will not cheat you.
Don’t be insecure and sad. Give focus on your studies and create your own identity.