Irregular periods!!

Stacey • Trying for baby number 2!
Since u had my baby (16 months ago) my periods are really irregular and have never gone back to normal. I am overweight so I no that's probably most of the issue but they used to be regular. I really want a baby and don't know when it's gonna happen! 
My last period was on the 1st-7th October. My next period should be on the 18th November according to glow but sometimes I just miss them altogether!
Anybody have any idea when I could have ovulated or be ovulating?? Or anyone have any ideas how I can help myself get pregnant (don't say loose weight please as this is something I'm working on) 
Thanks