I totally understand your pain. I have an area in the front that has been straighter than the rest for some time now.
I have been washing almost daily with a sulfate shampoo and the area is curling more every day. Just keep at it.
I went from 3c hair to 2b hair...and am sloooowly reverting back after one year and 4 Brazilian treatments.
A word of caution. The keratin does build up in your hair over time. Don't get it done too frequently if you want to keep wearing your hair curly. My recommendation is twice a year. Good luck!