Re: Latch issues at 4 weeks old
If all your lactation consultants say that he has a good latch, I might be inclined to agree, without seeing you of course, and would attribute the flattened nipple to a latch change after the baby is done. When my son pops off mid-eating, my nippling is full. When I let him hang out and suckle after he's done eating, my nipple is flattened and the sides turn white. Do you think that might be your case?
To improve your latch I would pick a day and ditch the bottles. However I would get the tongue tie addressed first. I had a pediatric dentist use a laser to correct my son's tongue tie. I would ask your Pediatrician who they recommend. But do not wait.
I was under the impression it wasn't a good idea to use a nipple shield when dealing with thrush. It creates a warm environment that cannot breath. Personally, I wouldn't use the shield unless you are using it to get a better latch. I don't like them. I feel like it's another thing to wean off of, however many women swear by them as the only way to transition to the breast. For me, persistence and waiting for the baby to have that lightbulb moment were key. It just takes time for some little ones to get it. I know that's not very scientific but they all have that moment where they are old/big enough and it just clicks. Both my son and my daughter wouldn't even look at my breast until that moment it clicked. For my daughter it was 3 months, for my son 3 weeks. Hang in there mama. It's worth it when it all works out.
If you obey all the rules, you miss all the fun. - Katharine Hepburn