Is it normal to like an anal finger insertion?

I am a regular guy who is strictly attracted to women. I love to have oral sex performed on me, probably better than regular sex. Some years ago, i had the pleasure of having a white woman perform oral sex on me. I have never been with a white woman in my fifty years on this earth and of course, like many black men wondered what it would be like. In the middle of this performance, this woman who was taking my entire penis with no problem, decided to reach under my sac and begin to play with my anus. At first just around the hole and then gently inserting a middle finger, then a thumb. By the time i came, I was squirming to insert her finger further into my behind. It was the best sexual experience i've ever had. Afterwards i discussed it with her and told her i've not only never experience anything like that, but i loved it. Since then, i have found only one other women who has done this for me and i continue to do this with her, despite the fact that i'm married. I've asked my wife to do this for me and of course she responded with the question of whether i was on the down-low or something. My question is....is this normal? Believe me, i have no desire to have a man's penis in my behind, even the thought of being with a man disgusts me, so as far as being bi-curious, that's not the case. What is it about that particular act that turned me on so much, and is this normal?