could someone tell me why the leaves are turning yellow and falling off?..ty

yellow leaves usually follow a period of drought
Lets say you have the plant inside, after it has been outside all summer.
Now with it in lower light, lower humidity than it likes, some leaves will drop naturally over the course of the winter. This is because the plant is not able to support all the leaves it had when everything was going good. When the plant sustains a dry spell or is put in a cool room it will react by dropping a bunch of leaves at once.
Check to make sure it is not sitting in water.
Water should not run straight through, if it does chances are the root ball has dry pockets and is not staying evenly moist.
Make sure the plant is getting 4-6 hours of bright light a day.
Don't overreact and drown the poor thing though.

If it is near a radiator then set a shallow dish of water near it, it may be suffering from a lack of humidity..or it could be a shortage of nitrogen, in which case buy some plant food pellets and apply according to instructions.