BFN. Should I re-test?

Ca

9-10 days DPO, do I keep testing or just call it for the month? This is my first time TTC and thanks to Mirena (recently removed, natch) I have no idea when my period is due. I had a positive OPK on 4/23, and have had spotting and cramps the past three days. Implantation bleeding or AF came early?