Hey mel and madb yep I expressed full time with dd, mainly attachment issues and she got used to the bottle. This time DS had trouble attaching at all the the right and a few dodgy attachments to the left had it bleeding and cracked so fast. The shields are helping so I'm happy to use them if it's the difference btwn bfing or not. Cause I have huge boobs and using shields I don't feel like we can go anywhere yet where I won't have my whole saggy H+ cup boozie out!
I had the exact same problem... But we feed fine in public with a shield now, not sure if it will help but here is how....

We were using a medela (?) one, which needed to be stretched right out and really suctioned on the the breast/nipple to work effectively. So putting it on in public was very awkward as it involves getting the whole boob out, I would do it with a wrap over my whole head and body! Lol

Then I discovered the Advent shield doesn't need to suction on as much, so now we use BFing tops with a good flap and I hold it between my fingers over the nip just as he goes on and his suck holds it in place! Then I can let go and sort my top or wrap or whatever.
I should mention I have big boobs as well