That is a tiny baby! Make sure she is thriving by taking her to the doctor for her checkups and weighing her at home if you can.

If it takes her an hour to drink 2 oz. maybe she isn't hungry. Switching to the number 2 is just going to make her not having to try so hard, make her eat more than she needs to get in one suck, and can actually increase her chances of getting a lot of air in her tummy. Or, Are you mixing the formula according to the package directions? She might not necessarily need to burp very time she eats. She might need a different formula if she is very gassy, colicky. There are special formulas that reduce colic, or you can get soy or lactose free.

If the gas drops aren't working, you can also try Gripe water, which I have found works very well.

Talk to your pediatrician about your formula and ask him which one would be the best to try.

I agree with mominashoe for Gripe water it help my baby too.

Hope it gets better for your baby by changing the fomular.