Loud knocking from rear at speed of tire rotation

My car listed above (5-speed) has been sitting in the driveway for the past week. When I got in it to go around the block there was a very loud knocking sound coming from the rear driver's side of the car. The sound was coming at the same pace as the tire rotation which made me hop out and check if I had a flat that was causing the rim to slam against the ground (the knocking is much louder than the sound of a flat slapping). All tires have the proper pressure in them. I drove the car around a little more to see if anything made the sound worse or better. The sound was louder when I was braking and seemed a little louder on the turn but continued at a constant pace when going straight and accelerating. The knocking is not occurring only when going over bumps which is all the information good old Google has been able to help me with. The "knock" could be a "clunk", it is very loud and disturbing enough for me to not feel safe driving (and boy have I driven some beaters before). In the driveway I looked under the car the best I could but have no jack. I could not see anything obvious. If I bounce on the car the is a pretty good squeak/creak coming from the rear driver's side suspension. Also in the driveway if I turn my wheel all the way from side to side when I hit the full extent of the turn I hear a grinding from the same rear driver's side tire. Any thoughts? I hate bringing my car to the mechanic when I don't already know the problem as it is a great way for less than honest mechanics to try to take advantage of a woman bringing their car in. Thanks anyone who can help!