How do I know when I can ttc when my cycles are like this? (Top cycle says 40’days to today but still no sign of AF so assuming I’ve not ovulated this month) My

cycle varies 19 days to 55 days. I’ve been off the pill for 3 years and not used condoms for 12 months and no pregnancy. Dr says we need to be dtd 3 times a week to be “trying” but it’s more like once/twice a week, sometimes more due to life, work etc... I’m a healthy weight, eat well, exercise lots, drink alcohol very occasionally and don’t smoke at all. What else can I be doing?