I dont think i am but im not sure........

I took a pregnancy test last month and it was negative but my period last month only lasted 5 days and was light. My period has always been very heavy full blown but last months was light and turned to a heavy spotty on the 3rd day. I haven't took a test since cause I haven't been really worried but until today and with my breast being very sensitive I'm concerned.......... Advice ladies is very helpful glad I have this app so can get information.............