I have started weight training, currently doing only half of what I used to do pre-op and for 30 minutes only, but by end of it I feel week and bit dizzy. I checked my BP when I return home and its normal.

I wonder if increasing carbs will help?

Worth a try. I also make sure I have protein both before and after a work out. Typically a drink before and either the rest of my drink, nut or a protein bar after. It takes away the jittery feeling I would sometimes get post workout.