How likely to get pregnant if you don’t have a period?

I have had the Mirena IUD in place since November 2017, and have not gotten a period since then (so according to my tracker on here, I’m near 500 days late on my period lol). I keep having these dreams that I’m pregnant. They happen about 2-3x a week. My last partner and I did not use condoms, and the last time I had sex was the beginning of March. I am just looking to know the likelihood of getting pregnant with an IUD and not having a period in roughly a year and a half.

(yes i know i can go get a test lol but for the future, how likely to get pregnant given my circumstances)