When to test after implantation

Amanda • I am 23, engaged to be married, our first is a beautiful 5 y/o angel in heaven, We lost her April 2015, miscarried our second October 2014, we are waiting for our rainbow after the storm. (Ttc 2yrs)
So I am pretty sure Im experiencing implantation today, due to cramping, headaches, and fatigue since yesterday Nd now also very light spotting this morning....if thats the case and I got implantation bleeding today when should I test?