Burning sensation in penis, no erection.

I had sex twice a day with my wife for about 15 days when i was on leave from office. On 12th day while having sex my penis slipped and had an impact aside my wife's vagina leading to pain and loss of erection but no swelling was observed. The pain went away and we continued sex a couple of times more for balance of my leave. My last sex was with her during her periods without protection. Then i came back for my office out of station. After a week I observed that my penis has lost erection and my morning erections which used to be hard are now very weak moreover i am unable to arouse myself and have erections. I contacted a urologist and he carried out physical examination followed by USG penis but everything came out to be normal. He is saying that it might be due to physicolocal issues and suggested me to deveiate my attention but still i always have burning sensation in my penis and slight pain as of like someone has pressed any nerves. I am afraid of any undiagnosed. Please help.