Irregular periods

I stopped taking my birth control august of 2014 and I finally got a period April of 2015. I had extremely irregular periods before I went on birth control. I'm so unclear as to why my periods are irregular I have had an ultrasound done and an internal ultrasound done. I've had blood tests pap smears done. But the answer is unclear as to why. My husband and I have started to try for a baby but with my periods so irregular how do I know if I ovulated or not or if there's not something more seriously wrong with me. More than frustrated :( anyone have anything similar to this with any answers