When to test ??

Ok im 12dpo and I think I'm experiencing implantation bleeding. I had pink streaked cm when I wiped just now . And earlier when I checked my cm I had a little clump of brown cm. my AF is due Friday . I have 2 children already but never experience implantation bleeding before . And my cervix is really high to the point where it's almost unreachable and its closed . So my question is when should I test ??? All answers are greatly appreciated !!