Two observable symptoms would confirm your problem:

1)  When you change your oil it appears foamy and chocolate colored.  Or,
sometimes, just removing the oil fill cap, you will observe that it has that
same foam inside.  However, the cap inspection could just show simple and
harmless condensation.

2)  As you drive down the road, even when the car is warmed up, if there is
a plume of white exhaust fumes following you, that would indicate water
entering your cylinders from the coolant system.

If you have either of those symptoms .. get it fixed, soon.