Niki
I totally hear what you are saying. Just as you overcome one obstacle with breastfeeding, and you're so proud and happy, another one arises. It sounds like your obstacles have been quite painful aswell! Congrats for making it this far.
Have you looked into the possibility that your LO might have reflux? The pulling off, crying, fussing, spitting it all back up can be symptoms.
You could try putting a hot compress on your breast or take a hot shower before nursing.
If you are still uncomfortable after your DD nurses, just pump a small amount. If you pump it all, you will tell your body to produce even more milk, and then you will continue the engorgement cycle.
Also, if your DD is having enough wet and dirty diapers, then she IS getting enough and you dont have to worry about how you'll manage. Growth spurts will lead to your milk increasing.
Lyn