U-Joint problem????

Help!!!

I think my u-joint is going out, but I'm not sure if it is that or something else. When I hit a rough spot in the road, the car almost changes lanes, it feels very unstable. Lately it has been making a noise in the back end, kind of like creaking metal, and sometimes it feels and sounds almost like I am getting a flat tire. Whoever had the car before me raised the back end, and the right front is lower than the left. Any ideas anyone? I would kind of like to know what it could be before I take it to an auto shop, I have had a couple of bad experiences with mechanics.:cry:Any help or ideas would be appriciated!!

Thanks, Bonnie