I myself am 30 & trying for my 3rd child but have irregular periods! I know your frustration. We've been trying for 4 yrs now.
Have you ever tried charting your temperature? It's really not all that hard to do. If you do a search for places to chart your BBT you will come up with places to keep track of your temps & you'll learn lots! Most of the places that allow you too chart online also have message boards & you will learn tons of helpful imformayion on how to tell when your fertile.

They will teach you how to track your cervical position, cervical mucus, & your temps will teach you alot about when to expect ovulation/Aunt Flow. I hope some of this imfo helpped?