A few weeks ago, my car stopped running as I was backing out of a parking lot. I added oil to oil tank (I am in desperate need of an oil change), and it started again. A couple of days ago, it stopped running again, so I added more oil. I then realized that my car was running because I accidently kicked the alarm on the car which prevents the engine from starting when enabled (very dumb of me I know). Anyway, I finally figured out what was wrong, and got in drove home. On the way home, a lot of smoke was coming out of the exhaust pipe. So much, I couldn't even see cars behind me. I put on my hazard lights because people kept beeping their horns at me as if I couldn't see the white smoke. I made it home, and saw a black liquid coming from exhaust pipe. I'm pretty sure it was oil. Also, the compartment leading to the exhaust pipe was leaking as well as it has cracks or holes. I'm hoping I just overfilled the car with oil? I am worried the engine might be ruined though. While driving, the car made a knocking noise, and it also seemed a little delayed on accelerating when pushing the gas pedal. Should I take my car to a mechanic or just to have a new oil change and see what happens?