I have a heat pump in my house. The living room, kitchen and front room, which are all towards the middle of the house have good air flow while the outside rooms seem to have little to no air blowing out.

Ductwork needs to be designed with the proper sizing based on the design air flow rates. The longer runs of ductwork have higher static pressure loss so the air takes the path of least resistance ie: out of the closest interior rooms. Most diffusers have balancing dampers and may need to be closed some on your interior rooms to force the air to the outer rooms. There could be some restriction or leak in the ductwork also. Bottom line, a qualified HVAC tech needs to look at your duct sizing, air handler performance and inspect ductwork, outlets and balance the system airflow.