Pain And Itching In Urethra, Double Streamed Urine And Burning Sensation. Could This Be An STD?

I am a 33 year old male and I am having an issue that I would love to get resolved. I guess it started in July. One day I went to use the restroom at work and when I urinated it came out in two streams for a couple of seconds and finally went to a normal, single stream. A lot of guys have this issue after sex or masturbation. Usually, after I have sex or masturbate, the first time I urinate afterwards I experience this. When it happened at work I didn't think much of it but then I noticed as the days went by it was happening more and more and more. Eventually I noticed that EVERYTIME I urinated it would start as a double stream for a few seconds before becoming a normal, single stream.

It has been almost two months and it is still happening but it is now worse. I am now experiencing pain and itching in my urethra. Not all the time but frequently enough to make me worry. It will itch every now and then throughout the day which I will have press on my penis to get relief. The burning is usually only noticable during urination and for 30 or so minutes afterwards. I am thinking that I may have Gonoreah (sp?) or Syphlis (sp?) or Chlamedia (sp?). I don't know for certain but I don't see any other reason for this. Can anyone give me any advice??