Ok so this is very common. Hair grows in cycles and during pregnancy, the cycle slows down so there's a period when the hair doest grow as much and look thin. There are lots of remedies that can help you restore your hair to its original healthy condition. Growth supplements are very good at helping stimulate hair growth. I use the collagen supplements from https://www.vitaminexpress.org/uk/collagen-supplements
. I have naturally thin hair but using this has helped with the hairgrowth and preventing hairfall. You can also try a volumizing shampoo for the time you're waiting for hair growth stimulants to kick in.