Check your lower control arms, make sure the ball joints aren't loose or the arms themselves aren't loose. The lower control arms control your camber, check to make sure the adjuster bolt, where the lower arm bolts to the subframe is tight and not loose. If those aren't torqued down they will rotate themselves from vibration. Make sure the Ball Joint holes on the arms aren't elongated either (you'll find out quick if your ball joint falls out)
Also check your trailing arm shock mounts for anything like this...This is bad, very, very bad.