The National Electrical Code requires that a ceiling fan can only be mounted to a ceiling box that is made specifically for ceiling fans. The State of Wisconsin goes further and states that all ceiling boxes be rated for ceiling fans. Even if the house is old, the code requires this special box.
This is a very serious condition that is caused by a loose or broken wire in your service or service panel. It is important that this gets repaired as soon as possible. It is best to call WE Energies and have them check the service first, preventing any charges. If they do not find any issues, call an electrician.
Lights flickering in a house is usually caused by a loose connection. Once the loose connection is found, it can be repaired quickly. Finding the loose connection, however, may take some time to find.