That site, from the University of California at San Francisco, is an excellent one and I've referred to it a number of times. I saw point #20 on their list was this:
If you have anal sex, we also recommend that you wait 2 to 3 months before resuming receptive anal intercourse. It is important to start slowly, because scar tissue does not stretch as well or as quickly as normal skin and is more prone to tear creating a fissure.
Sorry it's not easy to talk with your doc, but don't let his/her demeanor deter you from asking anything at all you can think of. Good for you for being proactive!