What Causes Pain In Penis After Sex?

im a 34 year old male 5ft 8in 12.5 stone in good health i had sex with a new partner 3 months ago he gave me oral sex without protection i have a sharp uncomfortable pain down the lining of my penis this pain comes and goes also on the left hand tip of my penis appears a red sore and when this happens its sore to urinate also the pain goes right down into my testicile i have had std checks also urine samples and have been in the hospital to get an ultra sound done to which the doctor tells me i have inflammation in that area she then ask me for a urine sample and this all comes back clear what is causing this unbearable pain if its not a std?? and how come its only come about over the last few months ??? i have a great deal of stress at the minute and starting to think this is causing this pain ?? please help going mad here