i think it is very admirable that you can actually recognize that you might be falling back into your old habits.. it's hard for most people to actually see what they're doing to themselves. but if you're anything like the rest of us, i highly doubt that you'll "get help on your own"...there is never going to be a time when you feel "sick enough" or "skinny enough" to actually seek help. i can understand not wanting to upset your family, but it would be better to take steps toward getting better with them by your side, instead of doing it alone.
i would talk to your mom...
or, i guess, wait until they notice your old behaviors are picking up again. :/