Hello everyone

Today I was 11dp3dt. I've been taking test for days and I thought I got two very light positives on Friday and Saturday (they were so faint you couldn't see a line if I posted a picture). Tested negative on Sunday. Today I had my blood test and beta were only 5 mUi/ml. When I came back from the hospital, I started spotting, sort of a brown discharge that doesn't look like my period at all. So the whole afternoon and evening went by: slightly spotting (and crying, of course). Is there a possibility for implantation to take place this late, while testing negative?

Experiences? I'm heartbroken.