Be careful that the rash isn't a yeast infection. If diaper rash creams aren't clearing it up, check with your doctor. My daughter had lots of trouble with yeast infections when she was a baby. We had to use an OTC yeast infection cream to clear it up. If the rash is raised and very red, it likely is a yeast infection.
Another thing to consider is the diapers you use. Is she ready for the next size? The diapers we had been using for our daughter changed how they manufactured them at one point, and they were worthless afterwards. They didn't hold as much liquid, and she immediately got a HORRIBLE yeast infection. We switched diapers, and went up a size, and got things back under control.
Her body also only reacted well to Balmex for a normal diaper rash. I tried every diaper rash cream on the market, but for her, Balmex really was the only thing that worked if it wasn't a yeast infection. My son wasn't as sensitive, so every child is different.
It sounds like the diaper rash is the biggest issue. Maybe go back to as much breast milk as you're able to, and supplement with bottles if you're not producing enough milk. Then once you have the rash under control, try increasing the formula again.