not doing well on losing weight .. on the protien drinks now

I am on slim fast low carb drinks to get ready for surgery doc recommened it and i had lost 9 of the 10 lbi need to lose but then they chagne my diabetic meds to actos and i gained so much weight back so i am so discourage and i hope i can lose the weght in less than 2 weeks i have been exercising and on the protien shakes for my meals .. i have only lost 1/2 lb now ugh ... i was 250 lbs and now up to 256 when they chasged my meds ugh ... like i can lose weight with w.o diabetic meds .. anyoine find once the protien started they started to lose the weight faster and how fast? help... lisa