You are NOT a bad mother, lets get that sorted first
YOU and YOUR baby being happy are the most important things.

You do not need to see a doctor to change over, but can be beneficial in case of reactions etc.

As for your milk, as it stops being used it will dry up. You may get engorged for a few days, cold flannels or cabbage leaves will help.

And as for brand, there is many out there, so take your pick almost. Look aournd online, google and search investigate your choices. We have used S26 Gold for both our girls.

Good luck, and WELL DONE for making it this far!