Anxious about dress fitting

Hi everyone. For those who have already had alterations done, were your dresses able to be let out if they didnt fit correctly? When I ordered my dress, I had lost weight due to being sick at the time. Since it was so far out, I figured I'd be fine as long as I got into a good routine eating and exercising. I did ask the shop to add an inch to my measurements because my weight does fluctuate due to having a chronic illness and being on and off meds that make me gain weight. But I dont think they did (kicking myself for not insisting more).

Cue to February when my dress came in. It BARELY zipped. I mean, it took 2 people to get me zipped, and man it was TIGHT!! No way I would be able to wear it all day. Since my wedding isn't until August, I was okay, figured I'd lose the weight over the next few months. Well, work and life in general got in the way and I fell off the boat a few times. I have lost some weight, but I'm not sure if it's enough. I go for a fitting tomorrow and I'm just hoping its better than Feb. I'm pretty sure I remember the woman at the shop saying they could take it out if need be, so that a little reassuring.

Sorry for the ramble, I think I'm just looking for some reassurance that it will all work out in the end. Especially because I have neither the time, nor money to get a different dress. That's totally not doable. It's this dress or bust basically. Any thoughts, suggestions, funny dress stories? Please share and thank you!