>>396456214
The soreness is because your muscles have gone so long without use that they've atrophied. Just wait until the soreness is almost completely gone and do it again. Your muscles will adapt quickly and let you exercise properly.
In the meantime, focus on diet. tl;dr maximise the nutrition you're getting out of calories you eat. Vegetable oil? No protein, no folic acid, no vitamin C, etc etc, but LOADS of calories. Sugar? same thing. So don't eat anything with added oil or sugar, and then weigh what you're eating so you know how much you're actually eating. 
Then limit yourself.