Should i switch my 2 week old formula to sensitive if she's having bowel movements every 2-3 days and spitting up and gas pains?

Possibly: If symptoms are severe enough especially with colic than you might want to try switching to a different formula. Try soy based as well as sensitive formulas. If those still cause problems try a more refined formula like nutramigen. Although sometimes infants can go 4-5 days between bowel movements normally. But they shouldn't be having severe gas pains and spitting up. Try smaller feeds too.