My firstborn had difficulty latching. I used a nipple shield and he latched on perfectly. After two and a half months of nursing with a nipple shield, I had despaired of ever feeding him without it. Then, one day, he knocked it off and latched on without it. Perfect breastfeeder from then on.
Last year, I gave birth to my twin girls (all three babies have been delivered via c-section.) One of them (the smaller of the two) latched on perfectly and went to town, putting on weight like a champ. The second born of the twins was nearly a pound heavier at birth, but she had difficulty latching. I thought "No problem. I've been here, done this before." I immediately employed the use of nipple shield and thought I'd successfully avoided the same problems. WRONG!!!
My darling baby girl lost nearly a pound of weight and was NOT putting it back on. I was pretty much ganged up on by doctors AND lactation consultants all protesting that I was not producing enough milk to sustain twins. So, they gave me a hospital-grade pump and instructed me to pump for 10 - 15 minutes on both sides every three hours in addition to nursing on demand. With twins, that was pretty much ALL THE TIME. My little one got two ounces of breast milk in a bottle fortified with 1/2 tbsp of a specific formula the pediatrician gave me. After she drank this, I allowed her to nurse as long as she wanted. (That wasn't what was recommended, but I am a rebel.) Eventually, after a couple of months of this Hell, she developed a strong enough suck that she didn't need the supplements anymore, but she still didn't latch without the shield..... until the day after she was six months old! I seriously did not think it would ever happen, but she did learn and it has been awesome!!!
She is the best sleeper of all my children. She much preferred sleeping through the night to waking to feed.
There is totally hope! Hang in there!