How early can a pregnancy test detect the hormone?

I went to the doctors for a yeast infection, turns out my iud had migrated. I was given a pregnancy test and it was negative. I got the iud removed and was told I have to wait till after my next period to get another iud inserted. I’ve been feeling nauseous, sick, and dizzy. I’ve taken 3 test in the past week and a half and they’re all negative. I feel like I’m going crazy because I feel like I’m pregnant but I’m testing negative. Could this just be all in my head?