Loose weight whilst on medication

Hi, I am a 22 female and getting married in August next year. I went from 8 stone 7lbs 2 years ago, then got put on quitiapine and mertazapine which is a anti psychotic that makes your appetite rocket, 2 years later and I am 12 stone, crazy right! I really wanted to loose weight before but the fact I am getting married now makes me even more determined. I really hope I can shift the weight within the next year, finding this app seems to be a life saver!!