Here is some helpful information about acheiving a comfortable and effective latch with flat or inverted nipples:
My doctor said I have inverted or flat nipples. Can I still breastfeed my baby?
Did you have any help with latch at first? Did anyone observe a feeding and offer assistance for achieving a better latch?
Has your baby's mouth and sucking ability been assessed by your IBCLC or pediatrician?
Do you feel like you have a lot of milk?
Could you please tell us how your baby's feeding/nursing pattern is now? How often are you nursing? How often are you feeding ebm? How often are you pumping?