Omg what doesn't change? So for me I was pretty slim before my first was born (still am), but everything sort of redistributed. My rib cage expanded and so did my hips to accommodate the baby...and they never went back to normal. It's minor but it affected my band size on my bra :/
Stretch marks: I barely got any and they're hardly noticeable but they're there. Not just on my stomach but on my thighs and boobs (I gained the ideal amount of weight with my pregnancy, so this was not from eating too much during pregnancy!!).
The stretch marks aren't the only thing that happens to your boobs. Sagging. It is seriously shocking. What was once perky now points down. Also boobs suddenly become VERY unsexy because they are literally bottles to you now. When they get so raw you can't touch them or so rock hard it's scary (when your milk first comes in) or leaks all over you during a family dinner with your inlaws...it sort of feels like your body is slowly betraying you.
Everything down below hurts and is swollen and foreign. I was afraid to look at anything for months. I got over it pretty quickly though because I had barely any tearing and everything went back to normal-ish quickly.
The hair loss. Oh my god the hair loss. Pulling clumps of hair out every time I took a shower. I had the receding hairline of a middle aged man and it WAS noticeable. Apparently this was also normal for most of the moms I talked to. It didn't stop until 9 months postpartum. It all grew back thankfully. Also my hair straight up changed. I had thick wavy/curly hair. Suddenly my hair has trouble holding a curl and is just sort of flat. Tried everything with shampoo etc...it's better now a year + later but it is just plain different. Also something multiple moms have now told me is normal.
Skin: some moms got horrific eczema all over their face chest and arms, others got their puberty acne back. My skin dried out and of course the under eye bags that come with sleepless nights with a newborn just never really recovered. I use concealer now for the first time in my life.
Then there's your clothes. You start dressing based on what can have spit up easily cleaned off of it. I was really into clothes before my son came along. You don't have the time anymore to care as much. Also clothes that felt appropriate before can feel weird as a mom. I have a baby face so depending on what I wear random people will assume I'm the nanny not the mom when I go grocery shopping with my son. Awkward. And of course your stomach takes quite a while to recover so you look 3 months pregnant for like two months postpartum...which is fun.
You can get back in shape though! With calorie counting and exercise (once my baby was weaned) I got back to pre-pregnancy weight quickly and actually feel pretty good about how I look now. Going out and getting a nice hair cut and buying some nice new makeup and clothes definitely helped ;)
TLDR: literally everything changes and if it doesn't physically change the way you feel about it probably changed. But you CAN get your pre-baby body back, it's just tough work!