Strange Mixture in my radiator Bottle

[tomiwa]

I have an OPEL OMEGA B 2.5ltrs V6, 1996 model. I found thick whitish colour emulsion in my radiator bottle, this appeared to be a mixture of oil and coolant. I notice my car overheats in traffic jams and when my AC is on. I also found out that both water level and oil level keep going down each time I checked them. I discovered as well that when I put on the AC, the green coolant drains out profusely around the Oil filter area. I made a few checks: no trace of water on oil dipstick, spark plugs removed show no water on their heads etc. Can anyone tell what to do to solve this problems