Coolant system problems on 323i. help please

I have a 99 323i and i've had some cooling system problems. The car was overheating once and I replaced the thermostat about a month and a half ago. since then it has been leaking a bit so i finally replaced the expansion tank today. The heater doesn't get hot anymore even after the car is at normal operating temperature. Is it possible that my head gasket is blown? The car runs very smooth and it doesn't smoke, has lots of power, but when it leaked coolant on wet pavement it was muliticolored just like when a car leaks oil.

If anyone has any input it would be greatly appreciated. Thanks!

Could definitely be a blown head gasket.

Do you change your own oil? The best way to tell if your head gasket is leaking is often coolant in the oil (or oil in your coolant, as you may be seeing). Next time you drain it, look for a milky sludge in the oil- if it's there it's coolant where it shouldn't be.

Can you find another point where the coolant system is leaking? Did the overflow tank fix anything?