how can i get rid of my double chin fast?

Grab your double chin with both hands between 2 fingers. Use one had if that's more comfortable. Using your hands, Shake your chin for 15 mins straight, 3 times per day. This increases activity level in your double chin and burns extra calories and fat from the chin. I know it sounds stupid but it works. Try it and you should see results by around day 10.

You should consult a good dietitian forthwith about your present problem.

If you diet, you should lose a big part of if, for the rest ( if there is), unless to have plastic surgery, you couldn't remove it. Sorry.