Breastfeeding tips?

My baby is a week and 3 days old. Every time I breastfeed her she always fights my nipple, moving her head away and is just fussy. She will latch on and feed for a few seconds and start moving her head away. I kinda have to force her to breastfeed and other times she will just fall asleep at my nipple after feeding for 5 mins. After fighting with her I just give up and give her formula. Any tips on how to keep her latched on or as to why she keeps fighting my nipple?