what does an HIV skin rash look like?

I recently got a reddish skin rash that resembles pimples on my back about 3 days ago.  And just today, i noticed the same rash on my side, so it seems to be spreading.  Each rash looks like little bumps of pimples all clumped up together, not spread out.  I'm really nervous because i just had unprotected sex with a female i didn't know about 2 weeks ago.  I haven't had any fever or other flu symptoms, but i'm in very good shape physically so my body is resistent to colds and flus anyway. I am scared and if i'm lucky enough to not have any STD, there's no way i will allow myself to be so reckless with my life again.