19 DPO - All BFN's

Corinne
19 DPO. Had a total of 5 BFN tests, last taken this morning. Heavy bleeding for 2 days 7-9 DPO. Possible very short period, implantation bleeding or chemical - how can I know? AF is usually 6-7 days, never has heavy as it was. V sore boobs, tired, headaches. Am I imagining it all or is there any chance?