Another way is to run way too rich....the leftover gas will sharpen your piston rings like razor blades and then bypass them....thus gas in the oil...what color does your oil look like now...and someone is right about doing a pressure check
My carb was dumping fuel really rich and my oil smelled like gasoline badly.
Once I changed out my carb and put new oil in I do not have that problem any more, but as mentioned above, a compression test never hurt anyone.