What Causes Delayed Period And Breast Soreness While HPT Is Negative?

Hi im 21 year old female, im relativly fit and healthy, I have never been on the pill me and my partner have been having un protected sex for four months now, every month i have had my regualar period the latest a day late and now i am 3 days late no sign of coming on. mild cramping in my lower left stomach area, sore boobs and i also have a yeast infection. i have already took teo negative pregnancy test but something just feels different. is there a high possibility that i am pregnant or maybe just all in the mind!