1997 Honda Civic 1997 Honda Civic Making Strange Noises

Noises problem
1997 Honda Civic 4 cyl Automatic 150000 miles

Hi, I have a 1997 Honda Civic and for a little over a week it has been making some strange sounds. It began with a loud metal grinding noise. Although I really don't know anything about cars, I would assume it would be the brakes - the only thing is, the noise does not occur when I step on the brakes, just completely randomly, while driving (not while accelerating or anything, although did first occur while turning left and then occured after that at any time at all). The grinding metal noise has not happened for a couple of days (even though it had been happening daily), but after that seemed to stop, a loud rattling noise began. I just changed the oil after the grinding noise began. The car has a bad history with the exhaust. When I first got it, it failed inspection for emissions and I had I think a new muffler put on, and perhaps a year ago, something in the exhaust fell out while I was driving, and that entire thing was replaced. It had the O2 sensor replaced as well. I know that I should probably get new brakes, too, if that might be a factor. The car also seems to idle slightly rough, sounds like a belt might be making some sounds and shakes a bit over 65mph or so, although I've heard that probably has to do with alignment, but the grinding and the rattling are really scaring me, I don't want any more parts falling out while I'm driving!