If I were you, I would call the doctor and let him/her know what is going on. She may be having a bad reaction to the new formula and you may need to switch again. I know when my son and my nephew had problems with constipation on a formula that was otherwise working for them, the doctor recommended 2-4 ounces of pear or white grape juice once a day. That little bit of juice solved the constipation problem.
Again, though, I would check with the doctor and see what he has to say. He may want to check her to make sure there isn't something else going on (like acid reflux or stenosis-- not sure what the whole name of the condition is... my nephew had it and it caused vomiting because the opening into the stomache was not open all the way. he had to have surgery to have it corrected). It is probably just the formula switch but it is better to be safe when it concerns your child.
The only other advice would be to do what you said you've already tried (give her 2 ounces, burp her, give her 2 more and burp her again, etc.).
Good luck. I hope that it stops for you soon. I know how inconvenient and worrisome it can be when they are constantly vomiting on you.