1998 Mazda 626 Car only gives luke warm heat and thermastat

Heater problem
1998 Mazda 626 4 cyl Front Wheel Drive Automatic

I have a Mazda 626 with 163,000 miles. Just recently I noticed the heat only gets luke warm. Not only that but on the temperature guage it barely gets above the C and when driving it drops below the C. To make matters worse the fan for the heater doesn't seem to be as strong as it once was. What could be the problem? thanks for answering