Help! Baby having trouble sucking

Okay so I just had my little girl on the 29th. We are having trouble with getting her to suck on breast or even a bottle. She sucks her bottom lip all the time. We even have an ultrasound picture where she was doing just that. Has anyone had this happen with having trouble sucking on either one. We're mainly wanting to express and bottle feed, but having a hard time getting her to suck anything.