Day of surgery questions

This may be a dumb question but do they give you undergarments on the day of? Or are you able to wear your own underwear but no bra? Also do they weigh you as soon as you check in or after your change into the gown? lol I only weigh myself after I shower and I noticed once when I weighed myself after getting dressed I weighed like 3lbs to 4lbs more. I just realized my last logged weight was without clothes so now I’m thinking maybe I won’t seem like I’m I’ve lost enough? I’ve lost about 7lbs so far a week into my liquid diet.