Why do i get a burning feeling in my penis, and why do my testicles hurt now and then?

I get a burning feeling in my penis when i urinate (go for a piss), its at the head of the penis, in the pee hole, and it burns alot when i urinate. I have no idea why it started happening. I also get alot of pain in my testicles, its happening awhile now, but only like once or twice a month. I've no idea whats wronf with me, i hope some of you guys can help me out. I need help right now :(