Circuit Breaker reading low voltage? (102-105 volts)
I am going with Ed Beal. Take a reading at the main lugs and see if you are getting a true voltage there. If you are reading between 118 to 126 volts to ground. Then if your meter can give you at least 1/100 of a voltage reading. Check the voltage between the main lug and the load side of your breaker to see how much drop you are getting. It should be something like .25V. If you are dropping 5 - 15 volts then your bus is probably burnt or corroded and your breaker is not making a good connection. 

If you are reading 105V at the main then you need to look further up line. Check with neighbors to see if they are having a problem. If not have the utility company check the lugs in you meter base. Look for loose connections or discoloring of the bus or conductors in the panel. Don't forget to check the entire circuit just in case there are multiple problems. Open switches, light fixtures and receptacles on the circuit and check all connections.

Good luck and stay safe.