Two days ago, I was driving to work and i noticed my car running a little rough. When stopping at a stoplight or stop sign, my car would shake and would also shake when the transmission was about to shift. I decided to wait till after work to check all my oils/fluids and when i turned on the car whiteish smoke started coming out the tail pipe. I checked my oil and my coolent and they seemed fine. I drove the car home (not knowing the cause) and the ride home i could see smoke when lights shown on the back of my car.

The next day, i turned the car on for about 5 mins and checked the coolent again. No smoke this time and no coolent loss or anything.

Today, i turned the car on for about 5 mins and left it on idle. Some white smoke came out the tail pipe, but then it stopped. I checked the coolent and it still seemed fine as well as the oil. I drove it for about 5 mins and left it running and still didn't see any smoke. I finally turned off the car and inspected the ground for leaks and did notice an oil leak. What could be the reasons for all these things?

Please help...
Thanks