DD4 is 11m, I went dairy free for 1m starting when she was about 3m old with no change but going wheat free* brought a change in her reflux in 48h, I then went on an exclusion diet for two weeks (turkey, rice, sweetcorn, apple & pear) and that seemed to 'cleanse' my body enough that she was able to drop her reflux meds.
Strangely enough DD4 is so sensitive to dairy that even holding beef brings her out in hives! No change from me not eating it though and I was super careful 
She also has had two TT revisions but really needs a 3rd, has an upper lip tie which means that no matter how we latch on, I still have vasoconstriction which can be painful at times and makes BF for hours flipping irritating as her latch is so shallow.
We've co-slept since birth as she used to have up to 7 hour feeds so I couldn't have done anything else! Though there wasn't exactly any sleeping going on on my part due to the pain & bleeding.
The failure part is because I am (was?) a bfing peer supporter and a trainee BFC. I haven't done any bfing support for months as I feel like a fraud. Nothing I have done has made any difference to how she feeds and I have done the lot - exaggerated latch/flipple, exaggerated latch with lip flip, biological nurturing, rugby ball hold, etc, etc - it still hurts so badly some times I feel like I want to peel my own skin off and run away screaming. Which makes me feel very lacking if I am honest.
*DD3 has a wheat allergy