why does my 17m old whine all day long?

[boobie]

i have a 17m old daughter who constanly whines, from the moment she wakes up to the moment she goes to bed. she didnt used to be like this she used to be a angel but now shes just moans and whines all days long, if she doesnt get her own way she has a screaming fit on the floor. day in day out she doesnt properly cry is more whining or fake crying with no tears for no reason what so ever. i dont know what to do anymore its destroying me i just want my old daughter back who used to be a angel. and when she goes to bed she just screams herself to sleep for around half a hour and screams when she wakes up in the morning. she seems to only be happy when shes out playing with other kids or in someones garden, but i dont have a garden cos i live in a flat and theres dogs downstairs. she hardly eats anymore and i dont get much help from her dad cos hes always on his xbox. oh and i have to go out like all day to keep her happy and when i do that shes only happy for so long, i dont have many friends or family with younger kids so shes just never happy anymore. plz help i dont know what to do anymore