Can implantation happen earlier than expected?

I was 4 dpo on Tuesday and had some craps in my lower abdominal/uterine area. After those cramps I went to the bathroom and there were a couple drops of light red blood. Yesterday (5 dpo) the cramps were there again but no blood. I know you're not supposed to implant until 6-10 dpo but not sure if it can happen early or if it's due to stress?