I do feel a little bit of heat from my heater

Any thing can go wrong with any part made, they are mechanical and carry a warranty, but they can still fail at any time. The cooling fan helps keep the coolant cool and not overheat, so that isn't the issue for no heat, if the fan wasn't working and the car overheated, the heater should work even better. If the water pump is circulating coolant at idle and all was good, the heater should be OK. If your RPM's are faster the coolant will be flowing faster, and that's when you say your heater works. If there is a restriction in the heater core, a similar problem would be a cause, but normally if you raise the engine speed the coolant is being circulated faster. In most cases the impeller could be an issue by not circulating the coolant as well at low RPM's. The cooling fan needs to turn when the temp is higher to help cool the engine. If the temp is normal the fan is not needed. Your blower is working correct?