2 months of trying to pin point ovulation

Hey guys! Still pretty new to charting. My OTK is still all negatives same as last month....Normal periods. ... I know last month I was way off on my ovulation dates...just a bit frustrated because it's day 19.... I really want baby number 2 before our son turns 6! Any tips? I've been checking CM too... no difference for me it all seems watery... lol I'm so confused!