She has trouble getting out of bed, dressing and carrying things - all jobs William has taken.
His mother said he was constantly striving to help, even when it meant missing out on things other boys his age enjoy, such as rugby practice.
"I'm always falling over which must be very frightening for William but he takes it in his stride and helps me get up," she added.
"One day I didn't wake up at all - my body had shut down from exhaustion. Despite being terrified, he phoned his nan and stayed calm until help arrived.
"If it wasn't for William I might not be here today. I honestly don't think I could live without him."
William and his mother Wendy talk about his caring
Williams is one of 10 winners from all over the UK to be recognised at the awards, now in its 35th year.
Among celebrities invited were pop group Girls Aloud, actress Catherine Tate, Strictly Come Dancing judges Len Goodman, Arlene Phillips and Craig Revel Horwood, former X Factor hopeful Rhydian Roberts and Match of the Day presenter Gary Lineker.
Woman's Own editor, Karen Livermore, said: "All our winners have shown tremendous courage and huge determination and we're delighted to give them the recognition they truly deserve."
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