I have noticed over the last week a sharp stinging pain at the back of the of my penis where the foreskin starts. It occurs only when my penis is erect and I clutch, bend or squeeze the shaft of my penis. The last time I had intercourse was approx two weeks ago, and before that oral, i recieved oral approx 2 months ago. I masturabate 4-5 times per week. Is this pain sexually related or something else?