The 'talking phase'

(Apologies for the long post)
So I was talking to a guy around April time and we were supposed to go on a date, but he cancelled and then pretty much ignored me completely until I saw him again in September. We were both drunk and I kissed him then and we text for about 2 weeks after that. We were talking pretty seriously saying we would give it a good go this time around and that we wouldn't want either one of us to see other people. Yet, we were supposed to go on another date in September and he cancelled as I was dressed and ready to go. I was so upset and hurt and he didn't text me the following day until I asked him why he wasn't speaking? He just replied saying 'well you haven't said anything either'.
Anyway, after this he asked if I was going to be out clubbing with my friends during the week and that was the last time I heard from him since September pretty much.
However, 2 days after he had cancelled my date I was so upset and went out with my friend for her freshers week and ended up spending the night with one of her guy friends.
It was a horrible mistake and I have regretted it ever since, but my question is, would you consider this cheating since we had just made clear that neither of us would be happy if the other saw someone else? More to the point, would you consider the 'talking phase' to be exclusive?