Implantation bleeding ! When should I test ?

Implantation bleeding occurred 10dpo and 11dpo (25th and 26th July) light brown spotting when I wiped with tissue and cramping. Has stopped now.

14DPO expected AF today no show. Took two test (boots brand digital 50MIU and £1 cheapie 20MIU) both negative one with FMU other afternoon urine.

I think I tested way too early as I only implanted about 2 days ago or so.