Implantation bleeding?

I haven’t had a period since my son was born 13 months ago. My husband and i just started to ttc again and tracked my ovulation this last cycle. I got a very positive ovulation test this cycle and we timed sex pretty well to conceive. I am 11 dpo today and started having brown blood on my underwear. I haven’t seen blood since the month before I conceived my son. I know that implantation bleeding exists but didn’t experience it in my last pregnancy. For those who have experienced it, how much blood did you see and was it around this time in your cycle? Or did my period just come earlier than it is supposed to come this month? So far my hpt is negative.