I'm in a similar situation to you. I'm getting married next May and have about 3 stone to lose too!
I've joined WW and have lost 5.5lbs so far, but I always lose heart (this is my 4th time re-joining), so I have to keep myself focused and motivated. That's why I signed up to this site!!
You can do it though, and it sounds like you are really determined.. Good luck x