how can you tell the difference from Implantation and Low progesterone

Been having random Heartburn , Bad headaches, Nausea and stomachaches. AF not due until may 18th had Intercourse during my Fertile window on May 5th on accident and not sure if I ovulated a day before May 4th or after. May 6th. HELPP!!!! Currently Day 6/7po (Never get these symptoms before AF always the day of and during the whole cycle)