A little over a week ago, I spent a day out on a small lake with several friends. This was not a particularly clean lake, and we even joked about getting things like giardia from urinating while swimming in it. About 3 days after the day on the lake, i noticed that urination became more difficult and burned sometimes so severely that I would gnash my teeth. At times the burn is less extreme, but I have now noticed a tiny scab like spot at the bottom of my urethra, abou the size of the head of a sewing needle. That was there for about 3 days, now there are 5 total timy scabs spread around the Glans and just above it on the penis. Do you think I have some kind of parasitic or bacterial einfection? Could I have contracted an STD from close proximity to others in the lake or swimming pool? Thank you,