Hun,
Early on we had 'so much trouble establishing bf. My dd would scream every time I put her to the breast for quite a few weeks. You're not being mean at all. I can't see your ticker so I don't know how old your bub is but try lots of skin to skin time not only when it's feeding time. what about baby led attachment? Lie with your top off and let bub find the breast. Could it be that by the time you feed her she is so hungry she wants her food then & there & is too upset to focus & attach? This was alot of the issue for my dd, maybe you could try feeding her a little earlier. If it's something to do with letdown maybe you could give her 10-20ml in a bottle & then put her to the breast when she's not so hungry and will be a bit calmer. Are your boobs to full for her to attach? Maybe express a little or soften the aereola between your fingers first. If she's really upset, pick her up give her nice cuddles then try again. Remember to stay calm, babies can sense our tension.
Don't know if any of that helps, just a few of the things we were working through.
Have you seen a lactation consultant?
You can still sort this out, don't give up