Should I have my dog rehomed?

Sadly I have been quite unlucky in life and suffer from an addictive personality. About 5 years ago I developed a debilitating chocolate addiction and my weight ballooned. I now weigh about 35 stone and am housebound and live a life of solitude apart from visits from my carer dropping off food. She suggested I should get a little dog for company and a year ago I took her up on her advice. I got a border collie called 'Shep' from the local rehoming centre. All was well but a couple of weeks ago I started having a recurring dream where I butcher Shep and eat her as delicious burgers. About a week ago I also started daydreaming of these events and it now consumes all my waking moments. I worry that my illness is entering a new phase - should I send Shep back to the centre or risk me turning her into lunch?