Irregular Periods

Taylor • 22 years old! TTC baby #1 with my husband!
I just started my 4th cycle of the year. My first one was Jan.31st-Feb 4th then March 7th-March 11th. Which is pretty normal 36 day cycle! But then I didn't have another one until July 4th-July9th and now Sept 19th-23rd. Where do I even start to figure out ovulation?