Struggling with feeding.

My little girl 12 days old, really struggling to feed which has definitely affected my mental state, I’ve been using nipple shields to help with the latch but even then can’t seem to get that right as on one side nothing comes out but if I hand express I have plenty of milk! Having to give the odd bottle now as worried in not giving her enough. I don’t think it’s talked enough about how hard breastfeeding can be. How do some mums just do it without thinking.