lost coolant very quickly

no there no any coolant on the ground and i checked the oil it's dark as usual no change in color :/

Do you get any smoke from the exhaust? Also, feel and smell the carpet in the passenger side floorboard. Wet? If the answers are both no, you could have a slow leak on head/head gasket/block. If the leak is small enough, it will be very hard to detect, just FYI. Try removing the radiator cap (inspect it while it is off) and starting the car. Look for bubbles, and keep it full. Also, don't let it sit and overheat while the system is not under pressure. Bubbles? You could also just have a VERY small leak somewhere in the system. Look EVERYWHERE and smell for sweet/coolant smell under when the engine is running or has just been turned off.