I'm so sorry that you are having pain and feel so frustrated. But it is GREAT that you know where to go/come for help and support. I completely agree with the above sentiments to get in touch with a local LLL Leader. But I also wanted to tell you that it is a good sign that the pain you are experiencing goes away a few seconds/minutes into the feeding. Your baby obviously had a bad latch or her positioning was bad in the very beginning if you've got cracked/bleeding nipples. It is possible that you've resolved that at this point though and the pain you are feeling is residual from those cracks.
Try paying extra special close attention to baby's latch and her positioning. Her being positioned even a fraction of an inch improperly can lead to soreness.
I really think you need some one-on-one help though -- you need someone to evaluate baby's latch and her positioning firsthand.
I hope you reach out further for some help -- you can get through this! This is something that is very easily overcome and you can do it. Keep your chin up -- you'll get through it!