Was what I did " unacceptable?"

I was in a relationship for about a year  and a half with this guy that i was so head over heels with that i didnt see the flaws. And since im at college, i only saw him twice or three times a month. But because of that it was easy to start to develop feelings for others. At the beginning of the relationship i told him about that. And he said " its fine as long as you dont order off the menu". Fast foward a year i hadnt seen him in about 2-3 weeks. Before that He had stayed up here for a week and a half and really got on my nerves. And i meet this guy.  Super cute, and i develop a major crush on him. Everything about him screamed " perfection". And well i thought it was a puppy crush so i just wanted to get to know him and become friends. And well the more i hung out with him the happier i got. I didnt tell my boyfriend at the time because i didnt think it was a huge deal. Minor crush and i didnt plan on acting on those feelings. Well it made me think about how unhappy i was in the relationship at the time. So i thought about it and i didnt find many things that i was happy about. Or that i liked about the boyfriend. So i break it off with him. 
Now the following monday he calls me and he had found out about this new guy. And he was angry, and he said " why didnt you tell me? What if we were married( which we weren't and he didnt believe in marriage) and he said what i did was unacceptable. This was a little bit over a month ago and his words still bother me. Even thoughh im super happy in a relationship with the new guy. I didnt cheat on him, i firmly dont believe in cheating, and i broke it off before anything could happen between me and this new guy. Was he right? Or am i just worrying about nothing.