Is it a possibility?

I have the mirena iud and I know they say spotting is normal but I’ve never had spontaneously spotting. If I did, it would get heavier and turn to my period and last 7 days. October 9 we had sex and October 20 I got light spotting (pink/pink tinged discharge) and it lasted to October 21 but it was just half the day. Haven’t had anything since I’m going to test in a few days to be safe but is there a possibility this can be implantation bleeding. I honestly can’t remember when my last period was either I know in September but can’t remember the days. I had it for a year now.