How would you feel?

My boyfriend is telling his mate ( who has a girlfriend and is over seas right now ) to live life because he's 18 and whatever happens over there stays over there. And asking if he wants to be single yet because he went clubbing for the first time there. Now I sorta feel like I can't trust him ? What do I do ?

He's going away in a couple of months to another state and I feel like that's gonna be his thinking. What do I do?