I would just query the ovulation timings you gave there? 19 days before AF? That would put people ovulating on day 9 of their cycle, and a much shorter cycle than 28 days. Most people tend to have a luteal phase of a fixed length, generally between 10 and 15 days, and this will always be the same irrespective of when you ovulate. So if one month you cycle is longer than you expected, it's because you ovulated later than you normally would.
This book https://www.amazon.co.uk/Taking-Charge-Your-Fertility-Reproductive/dp/0091887585 has lots of fab info in it - highly recommend it!