I think you're on the right track with the GV... I hope that works for you! Thrush sucks!!!
You mentioned boiling bras and I just wanted to point out that you need to boil/disinfect ANYthing that comes in contact with your breasts or your son's mouth. Burp cloths, teethers, toys, bibs...
Thrush is yeast so it likes warm damp places and sugar. So keeping your breasts dry, avoiding sugar and increasing your intake of yogurt (acidolphus) can help too.
Also make sure that you continue to take your treatments even after you start to feel better since it may take awhile to kick it if you've got a resilient case.