As you’re now on a synthetic cycle your old natural cycle is irrelevant, you no longer have natural periods so you’re not “due” a period anymore. Irregular bleeding is a normal side effect of the pill, and can happen at any time while on the pill. If you’re using the pill correctly and accounting for anything that can decrease its effectiveness like sickness and certain medications, you’re protected by the pill. If you’re not sure of your protection status then you definitely should be using extra protection.