Engine Oil Mixing with Water & Engine Oil in Radiator

hi my name is dominic, I am typing this because I have a 1996 Pontiac Firebird 3800 v6 I replaced the crank shaft and bearings due to the fact that they were bad while rebuilding my engine I replaced the entire gaskets and after rebuilding my engine and starting the car up, a couple of days later the engine ran fine until milky white milk shake residue started appearing on my old dipstick I found out that my oil in my water was mixing checking under the valve covers I noticed that the valve covers on the left side were a milkshake on but not on the right side I also found that the oil was in my radiator. there is also oil engine oil in my engine coolant I don't know if the pressure from the engine is causing the oil from the oil pan to push through to the radiator and through the cooling everythingis mixing. I don't know if it is my head gasket because all of my gaskets are new and the car has not been driven for more than 30 minutes if you can help me with this problem I be greatly appreciated.