Is it the norm to start off as fuck buddies and then have it fade away to the point where you're just friends?

I have this happen to me where we were fucking for like 2 months and then all of a sudden he said that he's having issues personally and he's just not feeling up to sex but we can still be friends. I asked them if sex was in the future and he said yes but doesn't want to talk about it. He does make off hand comments about one of his other friends, how people think that he and him are fucking and how they have definitely been fucking but I don't know if he's fucking him instead of me now. He said that I was good at sex and it's not me it was just him. Does this mean that I am actually bad at yet and it does nothing for him and it's all just lies, lies, lies?