Discouraged

Hi ladies.. new to the group. For you woman out there who have irregular periods how do you track ovulation & your fertile days. My cycle is anywhere from 26 days- 30 days. I had my period on March 11th & last month was only a 26 day cycle... it’s hard to track with the app because app states I get my period every 28 days so I feel the ovulation & fertile days are off.. any feed back would be great. I had my period March 11th & tried on the 20th & 26th but I’m being told those wouldn’t be the correct dates. Thanks!