I have taken since Nov 2012 under MD supervison Phentermine HCL 37.5mg, Phendimetrazine Tart 105 mg, Phendimetrazine Tart 35mg 2 tablets twice daily, Phentermine HCL 30 mg with NO results of wt loss. Now he has prescribed Diethylpropion 75mg ER, what are the chances that this will work?