Right dosage?

How do you know if you have the correct dosage to prevent pregnancy? After having my baby in 2018, I took BC. When I began breastfeeding less, my BC got messed up. Started getting my periods every two weeks. My doctor asked how often I breastfed, I said only at night. He changed my BC. Fast forward to now. Should I call and ensure my dosage is correct now that I no longer breastfeed? Had a pregnancy scare, and I started to rethink my dosage. Never questioned it before until now.