On Friday I went out got drunk and slept with my girlfriend. Saturday I wake up slightly hungover, no more than usual when I go out and showing signs of a fast recovery. Then between 2 and 3pm I start to feel cold develop a fever and had to go to bed for 2 days. Now I have uneven swelling on my shaft and a little by my perenium bone. Was it the drunken sex or flu like symptons

I've never heard of an uneven swelling of the "shaft" as a side effect of the flu so my guess will be rough sex... and perhaps you broke/ruptured something.