I had my menstrual on march the 4th it last only 4 days and I spot for 2.. My bf and I had unprotected sex on the 15th according to the fertility calculator the 15th is the second fertile day.. The 16th I spotted which has happened before but the 17th I woke up which looked like my period blood I even stained my sheets I've been cramping really bad and it's the 19th can this be normal? Is this implantation bleeding plz help..