I had my period April 4th-10th. My boyfriend and I had sex on and off but if I could guess a conception date it'd be the 16th. My ovulation was from the 15th-21st. Yesterday (April 22nd) I noticed some brown discharge that looked like old blood in the evening time, as the evening went on I experienced some cramping that wasn't as intense as menstral cramps that has continued to now. I still have not had a heavy flow and it is only spotting that is either light pink or has a slight brown tint in color, is it possible implantation bleeding? My period is not supposed to start until May 4th..