I know exactly how you feel. My baby is 7 weeks old and feeding is still a little painful. Like you I had sore cracked nipples that bled. I have suffered from mastitis, engorgement, milk fever and now thrush. I went through a stage of having to express and found it too time consuming and during the night, I wasn't getting any sleep.
After about 3 weeks, I tried the nipple sheilds and they were a godsend. But they started to hurt after a while. I found that Flynn wasn't opening his mouth and I was forcing the shield into his mouth, hence he wasn't attaching properly.
I've heard that shields can make your supply drop a little, but as long as you keep exclusively breastfeeding and not supplementing, you should NEVER run out.
I'd reccomend visiting a lactation consultant or midwife. It sounds like your attachment might need a little improvement. Also get them to check for tongue tie as this can cause breastfeeding problems.
Good luck and please hang in there with the breastfeeding.
Laneisa, QLD, 5 kids + baby Flynn 24/02/05