I dont understand

I had my last period September 2 it came a week after taking plan b so i knew i wasnt pregnant. then my October period didnt come and i had all the symptoms sore boobs, stomach and back cramps, nausea, food advision, very bloated the whole 9 yards but still knew i wasnt pregnant cause i havent had unprotected sex during September. Partner asked me to take tests cause i wanted to go out for drinks, i took 4 over the course of 2 weeks all negative. Still had the symptoms so by 7 weeks of constant symptoms i went to the doctors and got ultrasound done. when i got the results that i wasnt pregnant my period came that same day a hour after i left the doctors office. Like what is wrong with my body why did it do that? Did i subconsciously think i was and when i saw there was nothing it came? I dont understand how that happened doctor said it wasnt the plan b