White smoke coming from the exhaust not overheating

So we were driving it about forty five miles an hour and all the sudden white smoke came out of the exhaust. we pulled over the engine light is blinking we turned it off and I thought it was overheating. I checked the fluids water was fine, no oil in the water or water in the oil no bubbling when the engines running in the reservoir. I had a timing belt replaced six months ago as well as a water pump serpentine belt, so it is not likely the head gasket. the white smoke will disappear and reappear. it does not have much power up hills but seems to go fine on flat. it does not smoke until going up hills and it usually takes larger hills to make it smoke. upon looking at the exhaust I found oil in the exhaust pipe. it shifts late and downshifts rough. what is it?