afraid of falling?

Shoogabean23

This has just started this week, i put my 2 month old on her back on the floor on a big blanket, and she will move her arms and legs around for a little bit then all off a sudden she throws her arms out wide, like she is about to fall or something... she gets the most frightened look on her face and starts screaming. I comfort her till she calms down but she is starting to do this more and more! tummy time is getting tough! How can i make her more comfy on the floor?