I was born into sex. It was forced upon me. I enjoyed it don't get me wrong and I continue to do so even though it is somewhat of a burden. But to ask what age it was I began having sex is like asking a genius when he became a genius and expecting the the moment to be explained in exact detail. No, these aren't pertinent questions and I think you know that. Just take my word for it, I am sex and sex am I.
That's all than needs to be known by you or anyone else at this current moment in time.