Inconsistent Cycles

My husband and I have been ttc since January. It took a while, 9 months, to get pregnant the first time in 2013 but then I had 4 back-to-back pregnancies (miscarriage 4 months later an ectopic, 3 months later preg with 1st son, 5 months postpartum preg with 2nd son). I have been charting my cycle on this app and have found that I go between 28 & 35 day cycles so none of the ovulation predictions have been accurate. Here I am again, 4 days late with negative preg tests and a broken heart 💔. Any advice to try to regulate my cycle? I am planning to use an ovulation prediction kit this month for the first time and see if that helps.