Is it normal that i have never had a orgasm while receiving oral sex?

I am in my twenties, healthy and a active person. I love to have sexual intercourse and have tried many things. One thing that had always intrigued me was that no woman I have ever met that gave me oral sex has made me have a orgasm on oral sex alone. I've had 20, 30, 40 min experiences and nothing. But once we switch to having sex it can take less than a couple of minutes. I've had oral sex with many different types of woman i.e aggressive, timid, white, black, skinny, tall etc....
Is this normal?