Implantation signs?

I am 8 DPO today and yesterday and today I've had some light brown spotting every two or three times I use the bathroom (this has NEVER happened to me before). I've also had some very mild and dull cramping these two days as well. My nipples and breasts are tender (more so my nipples) too. I'm not due for AF until Friday March 20th. Is it possible I'm implanting or have implanted?