Wedding Dress

Hi guys! So I'm hoping some of you have some insight for me - my dress is beautiful. It zips up to about the middle of my waist and then it has all buttons going up. It's illusion lace with 3D oplaque flowers and sleeves. Ugh. I LOVE it. When I ordered my dress, I was a size 14 bridal and due to my grandpa passing and having a very difficult time with that I gained some weight and stopped working out and let it get the best of me. Unfortunately I gain in the worst areas (My bust and arms but more so my bust area and top half). So I am now a bridal size 16. The dress fits everywhere else but the 5-6 buttons in the middle of my back won't reach and can't button. Crazy how only 10-15 pounds is one bridal size difference. I am currently on Keto and doing great and working towards losing the extra 10-15 pounds. My wedding is March 2020 so I have 5 months and won't start alterations until January so I really have 3 months to lose the weight. However, IF I don't lose as much in my bust as I'm hoping. Have you guys ever had this happen and if you did what did you do to fix it? I'm curious if I can alter my dress back to be an open back? OR I can always just have it taken out. It has a 1.5 seam allowance on each side so it's gonna be able to be let out up to a total of 3 inches. I just hope it's not too costly if it comes down to this. If any of you have had any similar experiences, please let me know! Thank you so much!