Sad out of no where

Last year i lost a baby girl... i just had my rainbow baby boy. My sil just had a baby girl and I instantly broke into tears when i saw her. Will it always hurt this fucking bad? Like i love my son so much it hurts i feel guilty for feeling sad over not having my girl. Im so happy for them i love them and their baby but i cant stop crying it reminded me so much of what me and my husband missed out on. I would never say it aloud to anyone but it just hurts. Im almost scared to meet her and cry its so embarrassing. Grief is so weird idk why this is happening I absolutely hate the feeling. It has honestly taken me back a bit ive been somewhat depressed and sad over it all over again. I try to get up and play with my sons or clean or anything and I instantly just get sad again. Postpartum has been tough on its own so maybe its just that but idk. I had to vent a let it out because im sick of crying over them getting a beautiful baby girl. They are my family and im very much happy for them.