2002 Honda Civic LX overheating?

I bought this car and the dealer had its garage do inspection. I didn't realize they don't check coolant. So i put coolant and was fine for maybe three days. Tempature Gage was going up to red at stop, then back done when I push on gas. So I checked coolant needed some more, but there NO leak on ground. I have heat in car. And when I open cap in mornings coolant ozes out with pressure. Why? And how do I fix this problem of overheating?

No heat means no coolant flow through the heater core, so maybe a water pump or a corroded heater core. Do a compression check to confirm the head gasket is still good.

Try to bypass the heater core then see if you still run too hot.

You go to a mechanic and have them pressure test the cooling system to see if they can find a leak. If no external leak is found you next do a block test to see if the head gaskets are bad. In Wisconsin we have a State Law that makes a car dealer do a used car safety inspection before a used vehicle can be sold. It specifically asks if the motor has problems such as a cracked block or bad head gasket. Check what is required in your State. The dealer may be responsible for fixing it for free.