Help diagnosing 1996 John Deere STX 38 white smoke problem.

I have a 1996 John Deere STX 38 in great condition. It runs and idles good but when you start it up it blows some white smoke out of the exhaust. It clears up after a few seconds and idles well. Mows good then all of a sudden it starts losing power and thick white smoke dumps out of the exhaust. Sometimes it will then stall, other times the smoke goes away in 30 seconds and functions properly again. I added some oil because it was a little low and noticed some dripping from the exhaust when first starting. Basically sometimes it runs fine and other times it smokes. What do you think it is?

Blown head gasket if OHV, or possibly carb leaking and washing down the cylinder walls. Could also be water in the fuel.

Many have told me that it's prolly the head gasket but wouldn't it smoke consistently then? What does carb leaking and washing down the cylinder mean? I assume you mean that the float is stuck open and to much fuel is getting into the cylinder and the smoke is unburnt fuel?

Fuel mixing with oil on the cylinder walls