Confused..

Hey all!

So, August 24th, I started the pill after being on Skyla(IUD) for 3 years. I had REGULAR periods the whole time I was on Skyla. My last period ended August 28th, I didn’t have a period in September OR October. I stopped taking my pill completely on October 1st and still haven’t had a period. Does anyone know what this could be? I am currently TTC, but all the pregnancy test I’ve taken have been negative.