Doctor says not an STD, what is it?

I am not sure, sounds like syphilis, go to a std clinic, Your doctor should be testing you for every std because he is not correct about symptoms clearing and going. People with have random symptoms that last as long as they want. It all depends on your immune system. Contact ex partners and see if they have any symptoms or have had an std. Good luck and rap it up for now, you do not want to spread or get more irritated down there.