Sorry, long post but need help.

12dpo I took a test and it was negative. 13dpo (day before AF due) and today (day of AF) I have not any heavy bleeding like I do every period, all have had is light old brown bleeding. Where I would normally have heavy bleeding and need to change my tampon every 3 to 4 hours, today I changed it after 3 hours and the tip only had light brown spotting and now it has stopped. (Sorry for tmi). Anyone else had this and think I should test again? Do you think this could be late implantation and should I test again?