What is it when you start getting sort of sore/pimple on you bum.?

just wanted to ask about this because i know its an std which i%26#039;ve just picked up from a girl i just met not long in the summer, and now this is the 3rd time since July that i get these sores on my bum...before i go to the doctor ( which i%26#039;m scared of) i just wanted you to tell me something just incase the result is bad for me.|||Don%26#039;t jump to conclusions...see a doctor if your worries but its probably just a pimple, or more likely an ingrown hair. Maybe a cyst, also really common in people of all ages. It probably burns from all the friction of standing and sitting,just moving around. I wouldn%26#039;t say it%26#039;s an STD seeing as how this is on your backside and most STD%26#039;s show up on the front.|||probably just a pimple, or a rash.