When should AF come after an HcG injection and IUI?

I took Clomid (100) on days 5-9. I had a mature follicle on day 12 and had the HcG injection. I then had IUI done on day 13. I am now 16 days past HcG injection and 15 days past IUI. I took a home pregnancy test this morning and it was negative. When should I receive my AF or could I have tested too early?