it sounds like urinary tract infection. the most common cause for this is a bacteria called e.coli. it naturally lives in the intestine but when it enters your urethra and multiplies it causes these symptoms. you can easily get tested for this (peeing in a cup). the results come out in 1-2 days and the usual treatment is 5-7 days of antibiotics.if left untreated for long it can cause you pyelonphritis (a kidney disease). it could still be an std. get tested, go to a doctor AND DON'T WORRY TOO MUCH!
It could be an std, or it could be a urinary tract infection. You really need to see your doctor or go to a clinic. Leaving either untreated can cause a lot of problems.
Aj