Welcome to the club jahfreak
Sounds to me like your Doctor is not doing his job. Sorry to hear that. Your physical and sexual health is his job. I would call and speak to him one more time to seek the satisfaction your deserve and get answers to the questions you have for us now.
I might suggest you write things down in preparation for that discussion and take a witness if possible to the face to face consult. Failing success on that, find another Doctor.
Penal shrinkage is common for all the same reasons others have commented before me. Although it is a liittle early in your healing process to impliment a full blown penal restoration plan, it is not to early to have one. I see a couple of choices for you. Try to dig such a plan out of your present Doctor along with drug samples, for free, to test a little later. Barring success on that front, find another Dr. or make you own plan. I personally lost an 1".
On the subject of your overall recovery I wish to caution you to be patient and go easy. That might me counter intuitive to your nature but please go easy. You have had Major Surgery and the healing process takes far longer then we realize at the beginning of the journey. Those tissues are wet and take longer to heal.
The moderator of this BB has assembled a nice list of resources for your reading.
Here is the link https://www.healingwell.com/community/default.aspx?f=35&m=52996
You will find many answers to your questions by mucking around with those links. They are a marvelous resource.
On the pain in your butt. Keep things very clean along with a little extra skin care after bathing. It feels good, makes you smell better and promotes you getting familiar with how your body looks and feels now after surgery. A decent sized mirror would be helpful. Normal activities within reason are encouraged as we heal. Walking, swimming and mild exercise. Lifting is not encouraged till later but I want to stress all these activities are normally part of a Doctors orders to their patient. The fact that you have not had such normal conversations leaves me concerned. Caution is the word of day on these issues and proceding under medical advice is always recommended and encouraged.
As you can see from the humorous tone of some of these guys, if we don't laugh we sometimes cry at the devestating effects Prosate Cancer has on our minds and bodies and our families.
We hope to encourage you to do the best you can for yourself and for all who are around close you. We want you to succeed and be well. Please read the particulars of my closing signature block. We do that for a good reason.
Prostate cancer used to be a fatal diagnosis but during my lifetime has become less so. We want you to know you can still have a full productive life.
Are you the same NO. Are you OK, YES.
I hope this helps a little and please keep us up to date on your progress.
Best Wishes Jim