The check engine light is on oil is good coolent is good

Need to get a scanner to see what trouble codes are the ECU memory. Check engine light on dash is diagnosis with a scanner for this concern. More likely a sensor or sensors by the age of car are at the end of good performance.

did the vehicle over heat, a cylinder leak down test will pin point if you have a blown head gasket.

Usually if there are no external leaks, and you are loosing coolant, the engine is burning it out the exhaust pipe.

suspect bad oil pump or clogged filter

Generally speaking, if you have engine oil in the cooling system, you have a leak somewhere in the engine, which could be a head gasket.
Is there any sign of coolant in the engine oil ?

well without more information do what its telling you, after its cooled down check oil level, coolent level, break fluid, transmition fluid, power stering fluid, when checking the transmition fluid you may have to start the car and let the engine warm up, check owners manuel to be sure. and dont forget to check your air filter. all these thing should be labled under the hood. and remember NEVER check radiator coolent while car is hott.. MAKE SURE THE CAR IS COLD AND HAS NOT RUN.. usualy check it in the morning after the car has cooled down over night..

take it to autozone and have them hook it up to their pocket scanner, chances are you need a new gas cap but if thats what the scanner says you need to buy it directly from the dealer not from autozone

remove the engines oil cap and look at the inside of the oil cap.
If it has an amount of gel like pudding I call it inside the cap YOU DO have a coolant leak for it is mixing with your engine oil

it sounds like a bad head gasket if your getting cylinder pressure in the
cooling system + oil, odd's are there is coolent in the oil.
I would not drive the car to avoid doing any more damage also if it's going to be a while before you have it fixed drain the oil + all coolent
put in fresh oil + filter leave coolent drained run the engine for a minute
to circulate the oil this should minimize any rust from sitting.
sorry i don't have better news good luck

you might need a valve job