1998 Chevy S-10 Noises and smells- Am I safe to drive?

My car has been starting to make noises in the last two weeks. It almost sounds like the alternator, when it goes out, but I know its not that because that was replaced in february of this year. It doesn't do it every time I drive. It did it today and the last time was 3 days ago. It doesn't matter if its a short or long trip it still makes the noises. It'll do it both when i'm pressing the accelerator and when i'm pressing the brake. It almost sounds like when I'm in 4-wheel drive(and the roads are clear, like in the summer) and I pull into a parking spot and my truck doesn't want to turn, it makes a noise because its hard to turn.
Also I have a problem with my exhaust. It'll smell like rotten eggs, and even at times almost like propane. I know that there is nothing that should make it smell like propane but it does.