Yeah weeeeeeird stuff happens with all those hormones. Apparently your hair doesn’t really shed while you are pregnant so it gets all thick and fabulous (or if you are like me and have thick hair already, thicker and haystack-y and impossible to control).
Then it all falls out about the time you get your first period after the baby is born. So it might look thinnish for a bit. But then you will grow a bunch of new hair and it all goes back to its regular cycle.
It will sort itself out eventually, hang in there! If it’s looking really damaged (split ends etc) you could try Olaplex, which is a hair rebonder that can help repair damage.