The info your doctor gave you was as correct as we currently understand it.

Yes, there is SOME HIV in saliva, but probably not enough to infect the skin cells of the penis. There is a hell of a lot more HIV concentrated in 1 squirt of semen than there is in say tears or saliva.

There seem to be inhibitory proteins in the saliva which further impead the spread. The virus is pretty delicate, and after you have blown your wad, you usually pull out and either clean up or dry up. No conducive to HIV survival.

With receptive anal intercourse, i.e. almost the same thing as oral, just that the geography is a little different, you don't have the inhibitory proteins, the rectal mucosa is always going to get abraided, exposing more HIV to your penis, and more penile skin is rubbed against the gut wall than is going to happen when you are getting blown. (Teeth as protection from transmission??)

Obviously, it isn't fool proof, there are a few cases of oral transmission of HIV reported, but usually to the guy who is doing the sucking.

This at the moment is the best info I can offer. Dr. Danny