How do i stop my daughter from crying everytime i set her down?

i have a 8 month old daughter and starting just a few days ago, she completely changed. everytime i set her down, before she even touches the ground she screams like shes dieing. i cant even set her next to me on the couch to watch tv, she has to be on my lap. she wont use a bouncer or walker or anything anymore. much less play with her toys. she just always has to be held. why is this? the only time she is by herself is when shes sleeping or i give her some finger foods. how do i get her to be able to play by herself or sit by herself again?