That is not normal. Are you keeping the bedroom door closed? If so, try opening it and see if that makes a difference. Also, consider buying a device to measure that air flow through the supply duct, for about $14 from Amazon and compare it to the other rooms. Here is a link. Also, you should have a return duct in the bedroom that transfers air from the bedroom into the living room, when the bedroom door is closed. Make sure this return duct is not obstructed.
Amazon.com
If that doesn't show the problem, you may need to hire an HVAC technician.