I went from 170ish, down to 112 ish (ED related) and now I’m sitting about 130-133 depending on the day. My breasts went from 38DD to now a 32 or 34B. They definitely sag, they’ve always been a big saggy, but doing any exercise that targets the pecs help perk them up a bit. Bench press, and chest flies, incline dumbbell press. It won’t make them look like you had a breast lift, but building the muscle will give a bit more structure and minimal lift to the breast. My nipples point straight ahead. I’ve noticed with the weight gain that my breasts feel and look fuller than they did when I was 112. Still saggy but more volume on the bottom. The upside tho, is when I pms and my breasts get swollen, they look fabulous lol