Does not have much power and it drives rough

I was running errands the other day, when after my first stop the car was hard to start. I had to put my foot to the gas to get it to run. While driving it didn't have much power and drove real rough. Had the same thing on the second stop. When I got it home the back hatch area was smokey and the carpet over the muffler was melted and the bottom of the car (floor) was blistering hot. The next morning I checked the fluid levels and found all to be good except the oil looked a little thin and smelled of gas. When I started the car it cranked for about three seconds before starting. It does not smoke. Can anyone out there help out?