Ureaplasma can be naturally occuring, but gardnerella isn't. It's a bacteria that causes bacterial vaginosis in women, and isn't technically considered an STI, but can be transmitted sexually.
Your doctor should prescribe you some antibiotics for at least the gardnerella.
No need to be scared. Just go talk to your doctor and take the meds, and you'll be fine. If you have a recent female partner, you should tell her about the gardnerella. Untreated infections can cause serious problems for women.