Implantation question

So I’ve had two babies without ever experiencing implantation bleeding. However, I’m on the mini pill and are not trying to have a baby as of yet. I haven’t had a period since July and this past week experienced a light pink/ light blood kind of discharge. It wasn’t enough where I had to wear a tampon or pad just kinda was present in my underwear and somewhat when I wiped. It wasn’t brownish it was pink. My question is... when should you test if you experience implantation bleeding. I don’t know if I ovulated since I don’t get my period and have zero clue as to what this is. It literally lasted a day or two or this nonexistent bleed. Any input is greatly appreciated 💕💕