roughly 3 months i developed painful urination and a red spot on my penis shorty after having sex. the painful pee went away after taking antibiotics however the red bump is still there. i have been tested for all standard std including herpes, hep, and i have done a urine sample and everything is negative. also when this first occured i had more than one red spot and even a blister on the shaft. and the partner i was with right before all of this told me they had herpes. is it possible these are undetectable herpes since my test came back negative?