It almost sounds like you may have a yeast infection around your anus or or in your rectum..Go see a Doc bud...
Stinging urination can signal a kidney or bladder infection. Sexually transmitted disease is cause by a bacteria and also presents with burning urination. If your urine begins to turn light to dark brown, and has a foul odor, you probably have an urinary-tract infection that can include an STD. To confirm the mentioned conditions, you should get an urinalysis and maybe a blood test. I do not know whether testing for STD automatically shows in an urinalysis. A blood test can confirm an STD. The white-blood cell count will be high if you are infected. If your partner did not use a condom for anal sex, there could be some reason you are affected by the act. To save time and money, supermarket chains have small clinics within their stores. There is no physician present, but there are trained personnel who can collect urine and blood samples and send the samples to a testing lab. The charge is about $40. Look around where you live, and you may view 24/7 Emergency Clinics. These clinics do have a physician in store. The same urine and blood tests can be performed. Inquire about the prices before you visit.
Harrald