Odd Discharge...

Okay so I've been obviously searching on the internet (which I know is a bad bad idea) but they haven't answered all of my questions, so I was hoping I could get some help from this community. So for the past 3 days I've been really sore and irritated and itching down there, and the discharge is slightly yellowy green. From what I researched it is Trich but the thing I am confused about is that I've only ever slept with one guy and he has been tested and came back negative to all STI's. So I don't know if it is actually Trich or it's just me overthinking a yeast infection. TIA xx