Sorry about the set back- direct heat is really really bad, especially for fine haired type 4 hair whether relaxed or natural. In fact, in my year + of being a hair board person, I can think of only one person with 3c + hair who flat irons weekly and yet has long hair that's not super thinned out. And seriously, considering that i have my maxiglide, I was not trying to hear this either but the correlation is too obvious to ignore. Each time you put that flat iron on your head, you're disturbing the moisture balance of your hair, so that the cuticle (which was thin to begin with) gets messed up and the hair can no longer retain moisture. Resulting in splits, chronic dryness/brittleness and breakage. So if I were you, I'd drop the flat ironing once a week and really work on learning the rollerset (ponytail or regular). And what's the problem with bunning??? Because if you really want to get serious, you could start conditioning washing, applying oil or butter to your ends and bunning for awhile and then compare the difference in your hair. Just a suggestion...
Oh, I started a 5 month no heat challenge thread as well so I feel your pain