Boyfriend apparently flirted with other girls behind my back?

We've been together 6 months, but apparently he was at the pub the other day with his friends and was like "This pub is so good for meeting loads of hot girls" and was like scoping out the talent there. Apparently when we were talking/before we made things official but we were exclusive he went into a room with a girl at a party "but they didn't do anything." And then at new-years eve when I wasn't there he was flirting with another girl who was there and saying she was pretty.

Granted this was months ago, but what should I do? This is my first relationship. He hasn't actually slept with anyone else but apparently he was definitely "looking for girls" and flirting occasionally.

Updates
1 y
My friends say he's probably just not as dedicated to the relationship back then as he is now, but should I be worried?
Boyfriend apparently flirted with other girls behind my back?
Post Opinion