Not opening the bill doesn’t make the late fee smaller.

Late fees do not depend on whether you have looked. The amount grows on a schedule, interest starts, and at some point it is reported somewhere that follows you into renting a flat or buying a car. Avoiding the envelope works on the anxiety and does nothing to the balance. The thing you are avoiding is the only thing that would help.

Open everything that has arrived, today, and write down what is owed and when. If you cannot pay, call them and say so, because payment plans exist and are far easier to get early. Set the bills to arrive by email and look once a week.