Irregular periods - bodies are crazy!

Rosie • 22 years old, have been married for just over a year and have been trying since January 2016
Does anybody else suffer from extremely irregular periods? My last few cycles have been 7 weeks, 12 weeks, 5 weeks and 11 weeks. I have had an ultrasound and have been tested for Polycystic ovaries but everything is clear. Trying to work out when I'm ovulating is a really struggle and any advice would be welcome! Rosie x