Cul De Sac Pleasure

A while ago my boyfriend and I were having sex. He was penetrating from behind and hit something inside me, it hurt for a split second but not super painful. On the next thrust he "broke through" deeper inside my vagina. At first we thought he had penetrated my cervix but found that this is highly unlikely and would be quite painful. I read about a space inside the vagina referred to as the "Cul de sac". Has anyone else experienced this and if so how was your experience? I have been fantasizing about doing this again since it accidentally occurred. It was what I can only describe as mind-blowing, I was repeatedly orgasming, I couldn't tell when one ended and another began. It was pleasurable for my boyfriend also and he told me it felt really good for him and it was actually prolonging his orgasm.