WTF! '01 Isuzu Rodeo Making Dragging Noise Underneath?

This past Saturday night I was driving abt 40 mph and all of a sudden there was a huge clunking noise on the penger side of the vehicle. I immediately thought I hit something metal and it was caught in the wheel well or something. I pulled over and didn't see anything. I eased back on the road and it started again. It sounded like something had come loose and was caught. The faster I drove the louder it got, then it stopped. It stopped but you could still hear what sounded like a dragging noise under the truck. Yesterday, I drove it 50 miles out of town and it was fine except for the dragging. On my way back home, the loud clunking noise started again. Something is banging against the undercarriage but when I look under the truck I don't see anything. What is this banging and dragging noise???? The truck drives fine. No indicator lights. Help!