Why does my hip slip out of place slightly when I sit, & when I get up I have to pop it back in or it pinches and im unable to put pressure on it.?

Hip subluxation. This problem sounds like you get a slight movement of the hip out of the hip socket called a subluxation. This problem should be discussed with an orthopedic surgeon as these specialists focus on this type of problem.
It is not slipping. More than likely, you are experiencing intermittent subluxation of the acetabular labrum into the hip joint. Most often associated with a labral tear. Needs to be evaluated by an orthopaedic surgeon who specializes in hip arthroscopy.