Pressure

So my best friend's wedding is in March. She called me yesterday to see if there is anyway I could lose enough weight to fit into a size ten by her wedding.... Since the sizes run really small the actual mesurements for the dress would make me a size 8.... This is because she wants two certain colors. The one color is for the pregnant girls and the other color only comes in size 10 and below... I told her that I would try, but that would mean I seriously need to lose about 70 lbs in about six months... It makes me nervous because It isn't like I have a metabolism that I can speed up with excercise and weight lifting. I am on medication that acts as my metabolism and it is at one rate and it gets checked between ever 6 months to a year (Or if I start feeling sick I get it checked periodically) I told her that I would try, but I honestly think that the smallest dress size that I could get down to would probably be like a twelve... I quess I'll have to just dress with the pregnant girls if I can't make it. It is definately not going to be fun dieting over the next several months, it is a lot easier to maintain weight than to lose it and I am not looking forward to all of the holidays not getting to eat any of the good stuff :(