How do you know if...?

I have been talking to a boy i know recently over msn, he talks to me in quite a flirty way like..i say brb he says ok i say back and he says yaaay missed u lol :L ....and loads of other things but im not sure if theres something there or he is just one of those people who talk like that to everyone..any ideas on how to work out how to find this out?