Hi 2boofulgals, you are not a failure!
I was just going to ask whether your little one was gaping ok - apparently if bubs don't open their mouths wide enough they cannot get the nipple in the back of their mouth which can damage the nipple and also prevent bub from getting enough milk easily.
We went to a paed osteo, and turns out my baby had some tightness around the top vertebrae and some problem in the roof of the mouth (not arching the way it should) which prevented him from gaping properly...
(In the end we weren't able to BF (so I totally understand how you feel) but have been bottle feeding EBM for 6 months now.)
About nipple shields - I remember reading the shields we have now do not affect supply like the old ones that used to be around. ( I can try to find the site/studies if you are interested.)
Also, make sure you are using the correct size shield for your nipple. (If the one given to you is not the right size it can still cause excruciating pain.)
Good luck whatever feeding path you take. Whether you BF/EBM/FF the most important thing is that you are able to enjoy your bub