You don't need a good telling off, you've done a great job of that all by yourself.
What you need is a big hug {{{hug}}} and this:
YOU CAN DO THIS!!
Cos you can, okay? 4 months is oodles of time. So have a think about what keeps going wrong. Have you got food in the house that's going to tempt you? Cos if you have, throw it out! Okay, sounds drastic, but until you get yourself firmly into this diet, it needs to go. Secondly, is everyone supporting you with this, or are some people telling you that CD is bad? Cos it isn't, it's great--if you do it properly. But it is bad for you to keep going on and off it. Make a decision to go on it--and then stay on it! You need to surround yourself with positive people. Which is where this board comes in--everyone's great here. Everytime you're tempted to fall off the wagon, come and post on here instead!
I don't know if you've got a thread going on the diary pages--I took a quick look but couldn't see one, so forgive me if you have--cos posting something there everyday can be really motivating.
Actually, although it might seem a good thing to have an event to slim for, like a wedding, it can really get in the way, cos it just piles on the pressure. So how about, instead of concentrating just on the wedding day itself, important though that is, thinking about how wonderful it's going to be to start your married life slim? And how you're really going to be able to enjoy the summer this year, wear skimpy tops and short skirts, etc., etc.
And finally...
Believe you can do this (cos I'm not sure you do!) There are so many success stories on this board and you're going to be one of them, okay?