Pregnant hamster help!?

Okay so a week and a half ago i bought a hamster,Female and she was rather large and fat and i fell in love with her because of how big she was, i took her home and she seemed jumpy after 3 days, and then settled down, for around 3-4 days shes been running around her tank storing food behind her bed house, along with all her bedding and bits shes finding around the aquarium, my aqaurium is 3 stories high so she has lots of room, shes pushed all her saw dust and bedding onto one side on the bottom, and shes always behind her designated bed house.. her belly is huge but when do i expect the babies? i need help!