I know this might sound weird, but they make this special thing for inverted nipples, it looks like a horn and you put it on your nipple and it helps the nipple to get errict and it helps the baby after you do that latch on easier. you can find it on ebay. It's called Latch Assist. That could help you sweetie.
I've had the same issue. I tried a breast shield for a while and she was able.to latch on, but it was just too painful for me personally so I exclusively pump. You just have to work a little harder with the pump to keep up your supply
I used a nipple shield but didn't care for it... I had a meeting with a lactation consultant and was able to get some good advice and tips with posture that helped.