Breaking tides and going on like nothing happened

So me and my ex broke up in March. We tried to stay close friends or as one would say Friends with Benefits but that went down the drain when I said he was playing me and his girlfriend. But I had to be honest of how I felt. But anywoo after he basically cut the ties with me he basically said to go on like nothing happened and that we never slepted together or even had sex. Which mind you didn't bother me until he said that what we had is gone and that our tides are gone. So I have to go on like nothing happened. My question is why do I feel like he used me and why do I feel like that the love we had was never real?