implantation bleeding or period?

i was supposed to get my period tomorrow but i got it today. i have some mild cramping like how i get on my period and about 30 minutes ago i went to the bathroom and see a pinkish/brownish discharge in my panties. but when i wiped there was nothing on the toilet paper. im thinking this is my period but im not really sure. i usually wake up and thats when my periods started its 6 pm right now. is it old blood/my period starting or implantation bleeding? also my breasts have been sore for the past 5-7 days but that also happens when im about to go on my period. please help.