Any synthetic hormones will affect "melasma".
Don't be fooled the new IUD's release synthetic hormones. If you are already frustrated with your situation, save yourself more frustration.
In this case, perhaps you shouldn't start any birth control until you see the dermatologist?
In the meantime, check into supplementing with Essential Fatty Acids - EFA 3-6-9 as well as a sublingual liquid or tablet of vitamin B12, B6 and Folic Acid. This will not interfere with breast feeding.