I got asked to be in a wedding

Ti
So today I was askes to be a brides maid for a friends wedding in August. I will be 37 weeks pregnant tomorrow. Baby is due March 30th (this is my first). I understand everyones body is different. I will also be breast feeding for as long as I can. Usually I hear 3-6months is for the best...I guess a minimum. Anyways, I have no idea when there will be dress tryons/fittings. She says she will wait til I have the baby first. What I am asking is what is the likelihood, with good healthy exercise habits of losing  all the pregnancy weight as well as how long would you predict? Dresses can always be refitted but, just curious! How much did you put on before and lose after and how long did it take?