I've Been Worried. I've Been Having Odd Discharge And I

I've been worried. I've been having odd discharge and I went to the doctor and they diagnosed it as yeast, but its been two weeks and it's not better. They said I'll have to get std testing. I know it can't be a std because I was having problems before my boyfriend and I had sex and he's been tested. I've used tampons before while not on my period and I've also made myself bleed from tampon use. What is wrong with me?