Boys who move on right after you're broken up...

Okay so I was talking to this guy for all of two months, and we had a small argument which was so stupid I cant even remember what it was about... Anyways, he stopped talking to me right after it and like 4 days later he texted me saying that he has a gf now so he should just block my number.. And that was that. Keep in mind when we were talking he'd tell me he loved me and all that... And now im completely broken by it. Like how can you say you love a person and then just leave and jump to the next person after? Am I stupid for being upset over someone I wasn't even dating just talking too? Do you girls think he just didn't even like me to begin with or do boys just act like that?? Idk if this all made sense but I'd really like to hear some feedback about this from you ladies... 
EDIT: the girl he got with was his ex from a few years back...