Sorry this took so long.Our yellow Lab was paralyzed yesterday,and we were at Tufts Veterinary School visiting him.
As your engine runs because of the volume of the crankcase that does not contain oil pressure is created. If its not vented in some the pressure becomes extreme. Years ago before emission laws, it was vented directly to the atmosphere. Today its called a closed system where it is vented thru a positive crankcase valve or PCV. This allows it to enter the combustion, be burned and and exit the exhaust.
There should be a hose running from one of your valve covers to your air cleaner. At the valve cover should be the PCV valve, this is most likely what needs to be replaced.Open your air cleaner and there should be another small filter . If you have oil inside the air cleaner that's also a sign.
A PCV should be under $20.00,pop in pop out no mechanic. also check that the hose is not clogged. This hose my not go to the air cleaner, but it goes to the intake at some point.
I hope that's your problem. Check your oil!!!