Help! I got an ovulation test no idea what I’m doing?!?

Hey! I need help! I’ve been trying to track my ovulation periods of this app and Calendar. My husband and I have been trying to get pregnant now for seven months and No luck. I finally got an ovulation test but I haven’t started yet I find it rather confusing I’m not sure if I’m 21 days or 28 days what if I’m irregular? Is it better to do the ovulation test or do the basal thermometer? Stress does play a big role in my life do the work and life etc. maybe that has something to do with it? I got tested at my doctors I had internal ultrasound done everything looks fine I’m healthy as can be and so is he. Any suggestions? I hope to hear from someone soon. The more information and the better :-)