SMOKE FROM ENGINE AND TAIL PIPE

My car recently just went out on me. Today while driving my car it started making this loud noise almost like the sound of an lawnmotor. When I was pulling into my schools parking my oil light and check engine light came on, when my oil light came on I was a little surprised because I had just had my oil changed two weeks earlier, I wasn't shocked to see my check engine light come on because that comes on every so often even though I've had that checked out several times and the mechanics can't find anything wrong, but today when I checked my oil it was completely empty and the noise from my engine became even louder as I drove it the near by gas station less than a mile away. After I put bout 3qts. Of oil in my I let it sit for awhile before I started my car again, once the car was started it still was making the same noise. While I had the car in park I started to give the car a little gas and there was an big cloud of white smoke started to come out of my tail pipes and from under the hood of my car. What could possibly be wrong with my car? Oh, also I almost forgot my car was also leaking oil from what I think is the oil pan and the oil that was leaking was brown and the oil on the dip stick was still brown was there was no mixture with the antifreeze.