i have a protected sex on sunday but the problem is oral sex which she gave me. After 2 days seem there is blister inside the penis skin. i had checked with doc and he not sure is it std but he gave me a roxellin injection on my butt and antibiotic. there is no pain during urine and no itch at all. The blister only obvious when i pull down the skin and is just a small part of it on the inner skin. There is no sores or ulcers on the head. Today is already the 4th days and i very worry cause i don wan to caught with std. Please help me out.