When would implantation happen?

Period is due tomorrow the 31st. On the 24th one week before period is due I had the faintest of brown spotting on toilet paper. Only twice that happened that evening. I have NO cramps, no sign of AF. I am tired I wanna lay in bed but can't sleep well. Lots of insomnia which is not like me. 
I guess I wonder if what I saw the 24th could be implantation. Anyone else have this? What were your signs?