Why are my tests negative?

my period is late this month.(i usually get it at the very beginning of the month) my last period ended around oct 8th. on oct 19th i have a weird bleeding, that didnt look like a period. it was like a light brown color. that lasted for about a week. after the bleeding ended, i had light cramping for a day. and after the cramping is when my started to become sore and my are very sore and sensitive. i have never had any of these symptoms before because i am only 18 and i never get pms symptoms when my period comes. i have taken 2 pregnancy tests and both had come out negative. should i wait a few days then retest?