Confused? Where is my period?!

[KW89]

We are TTC #3 I came off the pill (zelletta) almost 6 weeks ago (I didn't have periods on pill as took it continuously).

Baby #1 took 6 months to conceive and I had regular periods as soon as I came off of the pill.
Baby #2 was conceived within 3 weeks of coming off the pill and I can't actually remember if I had a period before he was conceived :/

I had what looked like an implantation bleed 10 days ago (discharge with a pink stain, only when I wiped, this happened twice in one day, but then nothing after, definately not AF)
I tested 4 days later, and again yesterday, but tests are saying negative....
I've had slightly sore boobs, which is the only early symptom I had with both my boys. Could I be pregnant or would it be showing on a test by now if I was? If not then where is my period?! I was always regular before going on the pill before I had my children, and I normally know that it's coming, lots of bloating etc, but there is no sign...