Sleeve dilemna!

I bought a strapless ball gown and am going in for my last fitting - I’m not at my goal weight unfortunately. I wanted to have my seamstress add sleeves and originally was going for off the shoulder, but was told three quarter sleeves are the most flattering for bigger arms. The other issues is that my dress is fitted around the abdomen and I can barely breathe in it ( last time I went in to try it on, I kept telling her I couldn’t breathe and she said I would get used to it, but also told me to sit down because I was looking pale and like I was going to faint), so it will have to be taken out some so I can breathe comfortably!

Basically, I’m stressing a bit because I’m already nervous about the day. It’s a rather big wedding and so many people I don’t know will be there so I’m getting some stage fright. I just want to be comfortable in my dress since I’m already going to be nervous. 😬 any tips for making it look nice but also comfortable?