Advise please

Shravana • Blessed with baby girl 11/1/17 😊
Hi ladies,
My last cycle - May 20 - CD 1
Started Clomid 100 mg - May 22 - CD 3
Positive ovulation test - June 8 -  CD 20
Day 21 Progesterone blood test - June 9
As per my blood test results on CD 21 the value was 4.04, which shows I haven't ovulated till that day but my opk was positive just the day before so possible I might have ovulated after my blood test FX. 
Today, I am 15 DPO. I started my periods but only see little amount of blood when I wipe and also noticed a streak of brown-colored blood. No heavy flow at all - my pad is all white but I see blood only when I wipe. 
I took a hpt yesterday which was negative. 
Now, my question is 
Would this be implantation bleeding and is it possible that I got a BFN yesterday as my levels might be low ?
Is it that once you have implantation bleeding, for sure you get a BFP

Glow Resources

Let’s Glow

Glow is here for you on your path to pregnancy

Glow helps you navigate your fertility journey with smart tools, personalized insights, and guidance from medical experts who understand what matters most.

25+ million

Users

4.8 stars

200k+ app ratings

20+

Medical advisors