Keep up the confidence! If it doesn't matter to you, it will not matter to her!
Any time you invasively enter the human body you generate scar tissue. I would guess that what your feeling, during intimacy, is a result of the scarring from your abdominal incision(s) and the cord structure scarring from your vasectomy. Any one of these or a combination of them all can be causing the sensation you have described.
In answer to your question, after my second conduit procedure, I did experience similar sensations from my midline abdominal incision for awhile post-op, but this pain did go away with time.
More recently, after a right side Inguinal hernia repair, I suffered a rather sharp, almost unbearable, stabbing groin pain that radiated from my umbilicus downward and across to the inguinal region right down to my right "man berry" which I thought would explode at any second! This pain was doubled during intimacy (ejaculation) and lasted for several days. Good news is that the pain is gone and all was well again in a short period of time!
So hang in there and "exercise" the area as often as possible (as tolerated).
Practice, practice, practice.........wink ; )
Your Doctor is right, the pain will go away with time..................and use.