He won't be talking to other girls at the same time. Yes, there are some guys who like to keep their relationship private, but most dudes who want a girl to be their girlfriend will make a point of introducing her to the people important to him.
and then he'll reappear, act super sweet, and ask you to hang out. Guys don't say this stuff if they really want the opposite. If you guys go out and come back and hook up, and sometimes have hangouts where you just hook up, that's fine.
To some of you this may appear great; to others maybe it's a nightmare.