grand prix is shaking and a wierd noise is coming from under the car

So maybe 3 days ago I was going to stop at a stop
sign and the car starts shaking. I go around the
corner and when I start to give it gas or shakes
pretty bad like it's going to stall, smells bad of
something close to exhaust. I pop the hood and
the engine is shaking look under the car the
exhaust and everything is shaking. I'm not sure
what it is.