I have a 14 month old so my heater is set at 70. Sometimes it does not kick on until the thermostat reads 68 and takes a while to heat the house. I have a 1900 square foot house. Also, some rooms seem colder than others. Is that normal?

Pretty much, 2 degrees out of calibration isn`t unheard of for the tstat. As for some rooms colder than others that could be caused but not enough insulation,, leaks around the windows,, windows not being up to par as far as double or tripple pane for extra insulation. Also the supply vents could be the fartherest away from trunkline /furnace ,might need an extra supply vent,, Also someone should inspect the supplyducts for leakage of supply heat,conntact your local power company and ask if they do inspections that might be of help for conserving heat and electric

It is a heat pump system and sometimes takes forever to get warmed. We do lose heat around the windows and the doors.