I have a 94 Civic that I have to keep adding coolant to. I havent noticed any leaking or spots. Any idea what could be causing this?

 

how much do you have to add? pint, quart, gallon?
how often do you add it , every day, week, month?
first thing i would do is go around & tighten down the hose clamps

 

If you do not see any wet spots in your engine bay, under the dash (heater core) or under the car then your car may have a bad head gasket which will allow coolant to leak into cylinder. Pull your oil dipstick and see if it is wet or watering. You will be able to tell if antifreeze is mixed with oil and if that is the case then you may have bad head gasket. When you change your oil, drain the first quart into a clearor glass cup and let it set. Water always sinks in oil and if you see that then you know where your coolant is going.

I have seen one car lose coolant because the thermostat was stuck close and it got so hot that it expanded out of the coolant reservoir tank.

 

I've just had massive issues with piston rings and blown head gasket (just did a full motor replacement). After swapping the head gasket twice and I was still losing coolant in my oil, I assumed it was a cracked block from overheating and bought a new motor. Check your radiator and coolant reservoir also for oil. It'll be a milky color if you have a blow head gasket or block problem. Also, your water pump may be located in the timing belt circuit. My 89 was spewing from a "weep hole" in the water pump. It's designed to leak when it goesbad. You'll notice fluid from behined the timing belt cover/below the crankshaft if this is the case.