PLEASE no bashing! I'm not trying to sound selfish!

I just found out I'm pregnant with my second baby. I'm only around like 4-5 weeks. I haven't even had my first ultrasound. I was supposed to get married on June 11th, 2016 but we postponed it because we decided to buy a house. We rescheduled a small wedding for September 23rd of this year. I tried on my wedding dress and it's too small! I can't afford getting it fixed because it's like $200 and they can't do it in so short of time. I'm thinking about trying the 3 day military diet. If I only do it for until my wedding, would it be safe? Again, PLEASE no bashing. I'm honestly not trying to be selfish!!!!