Agree with above...definitely sounds like a fungal infection, not that uncommon in uncircumcised men. I am sure your Dr gave you an anti-fungal, which is the appropriate response.
I will say this, while I don't think what you describe is a STD, it's never a bad idea to get tested to know your status. Many things can be asymptomatic.
Why not just get tested if that's your concern? Its a possibility, but its also possible its a fungal infection from not being able to clean it was well as you should.
AJ