DDCC from July. Hugs Mama, not something a new mama should have to deal with.
I had something similar after my third baby when he was about 2-3 weeks old. I wore him in a pouch (KKAFP) while shopping and I also wore pre-pregnancy pants that sat a bit high on my waist and buttoned too tight and by the end of the day, I felt like my insides had dropped too. Mine turned out to be a collapsed front vaginal wall, not uterine prolapse.
I found the WholeWoman site
and spent a lot of time reading, corrected my posture, both sitting and standing, and it gradually got better. Posture is a HUGE issue leading up to pelvic organ prolapse of any kind - even for women who've never been pregnant (and even for men.)
I was nervous going into my 4th pregnancy and birth but everything was fine! The initial issue had resolved and never reappeared after birth. Now I'm pregnant with my 5th and am not worried.
Your description of the belly binding sounds so much like my tight-waisted pants + pouch with baby = pushing everything in and down. Low-waisted pants that aren't tight are really the best idea for women. And *never* tuck in your butt & suck in your belly, as we've been told for so many years. Gotta have that natural curve in our lower backs.
Remember that Katy Bowman interview
a while back about how Kegels are BAD for your pelvic floor? She's a great source for info on proper posture preventing and correcting pelvic organ prolapse too.
I know it's hard not to worry, but things often get better, especially if you correct your posture and are careful not to strain. No crunches/sit-ups (EVER - for any women!), take magnesium citrate if you get constipated so you don't have to strain, and rest with baby.
Hugs mama & congratulations on your new baby!