If you’re not currently having a period, I would test once every week for a period of three/four weeks. If you do have your period, count the days since your last period. If it’s more than 25 I think you should be able to accurately test with an early detection test
If you’re not currently having your period due to breastfeeding you could check once every week or every other week! You’re super fertile postpartum!
If you don't have regular periods then you won't know when to test. You can theoretically get pregnant without having a period as ovulation comes before period, but if you're not having regular periods it's unlikely you're ovulating. I would test every 3-4 weeks if you're not having a period