Advice: I Think I Have an STD?? Read please.?

Ok, this may sound confusing so I'll try and be as simple as possible.
I've had sex (intercourse) with this guy only twice ever, and only in the last week or so.
He's just told me that the last girl that he slept with has 'something' and yes, he gave it to her. But the last time they had sex was ages ago and I know this because the guy is one of my best friends, and I know he's not lying.
Also, we're CERTAIN that he gave it to her, (not that she slept with someone else and got it from them).
So now I have to go to the doctor and get tested and I want to know what the doctor will do, and if they will be able to find something.
I'm worried that I might have something and they won't be able to find it because [the other girl] has ONLY JUST FOUND OUT/realised that she had it, and I only had sex in the last couple of weeks.
Is this time too short? Do I need to wait for it to develop or something? I'm scared because I don't want to get sores or anything like that.
Any info/advice?

go in asap

don't be stupid...see a Dr. ASAP

don't be scared, go to your regular doc or local clinic and get tested . worse case scenario .a shot of penicillin and a week of abstinence