How do you determine if it's implantation bleeding rather than your cycle? My last cycle was 9/28 -…

How do you determine if it's implantation bleeding rather than your cycle? My last cycle was 9/28 - 10/2 ( duration sometimes varies. ) Had an protected sex with boyfriend around the 16? 17? ( not exactly sure ) of October then about a week later starting experiencing what felt like round ligament pain in right ovary ( googles sytoms ) for about 3 days. Figured I was ovulating being that my nxt expected period was coming up in two more weeks ( 24-29 ). By the end of the month, still no cycle. Here it us now November 17 & over the past couple days or so I've been spotting. It started as brown discharge then light pink then bright red. Put on a pad thinking it's my cycle but just went to restroom & it's just a little on pad & when wiping light pink on pad. It doesn't seem to be getting heavier because it's already been 3 days of this. I've already taken 2 pregnancy tests & both negative. We're not trying to conceive nor preventing it just need to know so we can go from there. Any mothers experience something like this?