Yes, once your thyroid levels are normal you can always plan pregnancy. Always inform your doctor about it so that the treatment can be optimised as per the recent recommendations and norms.
Your doctor will most likely change your dose of thyroid hormone once you are pregnant. That’s because you need more thyroid hormone during pregnancy. They will also measure your levels of thyroid hormone 4 weeks after any change in your dose, and at least once during each trimester of pregnancy.