weight loss help

Hi, I'm 31 years old and weigh 175lbs and 5'6 tall. My normal weight that I was happy with was 145-150, I am getting married in 5 months and would love to lose ATLEAST 10-20lbs. I am a smoker, soda junkie and love eating BAD food. This is where my weight came from AND also from not moving around as much. Is there anyone out there that's a fitness trainer or knows SOMETHING about weight loss? I'm motivated to lose weight but am confused on what I should do. Thx