Sudden irregular periods & TTC

So, up until a month ago my periods were regular. Maybe a day or so variation at the most. My period in September was 10 days late. It was September 17-21. I completely missed my period for October. I'm not pregnant, not eating differently, or under unusual stress. I've recently begun to suspect I may have issues with my thyroid. My husband and I were hoping to start trying for baby number three with my next cycle. Has anyone else experienced this? How did it turn out for you?