So I got off my birth control in January and my body has not yet gotten back to normal. My periods…

So I got off my birth control in January and my body has not yet gotten back to normal. My periods used to be very long an heavy, but now they are very short an usually pretty light. Some days within my cycle I don't hardly bleed but the next day I'll bleed quite heavily. I'm really worried we are going to have a hard time predicting my ovulation window an it'll be a little more difficult to get pregnant. Any tips??