please please comment and help breast milk

So i have tried latching since she was born (a month) and she never has so i have pumped milk and never gotten enough through pumping so i have had to top up with formula she has 50/50 at 120ml  all up. So today exact 1 month she latched to my nipple shield!! It really hurts and she stopped after about 3 minutes and was defiantly getting some milk. Then she was acting desperate for milk, tried to relatch and she was acting like she was angry and wasnt gettigg any. So i have given her a top up on formula/ breast milk. Is it too late ???? Is it supposed to feel like knifes slicing my nipples when she drinks ??? Please please comment an help