My 91 buick regal is losing coolant ,can't find where coolant is going, the car is not overheating

run a can or two of coolant system cleaner through your system and flush

Any evidence of coolant in the oil? The oil will have a milky brown appearance on the oil dipstick.
If the engine is a 3.1L, the intake manifold gaskets are a well known problem. Aftermarket gaskets are a better fit-not so prone to failure. There would be driveability issues -rough running, poor idle, etc.-if the gaskets are bad.
How much coolant are you losing? Any problems with overheating?

Sounds like a blown head gasket.

Wipe any coolant off your engine make sure there is coolant in the car. Run engine for a bit. shut off engine and look for wet spot. Before this see if there are any cracks in rubber hoses or they are loose. It could be a thermostat gasket or warped housing to. Its hard to say without seeing it.

Check all around the intake manifold gasket for evidence of antifreeze. Also check your oil for evidence of coolant. The Dexcool antifreeze used in GM engines can cause the intake gaskets to deteriorate causing coolant leakage. Very difficult to detect.

First things to check would be fuse(s) at dash & under hood, as well as rad fan relay & possibly coolant temperature sensor.

You need to replace the intake plenum. Are you losing coolant too?.

Sounds like your car is overheating. If you have a temp gauge it should show that. If you just have an idiot light, by the time it comes on it's already too hot to operate. AFTER the car is cooled down, open the radiator cap to see how much coolant has been lost. Chances are there is alot missing. Add WATER (no sense in adding coolant if it's going to leak out) and idle the car at home. Look underneath as it warms up to find where the leak is.

Replace the coolant level sensor.