2 year old with 'Chronic Constipation'

My daughter will be 3 in September, and we have been batteling with dr.'s since she was 6 months old with her constipation problems. she is currently taking 1 capful of miralax a day, however she seems to have no urge to have bowel movements until she is extremely backed up and then she will scream and cry in pain. Her stools will be extremely large around and will be rock solid. She doesn't sleep well at all and also has dark circles under her eyes that tend to disappear when she has been 'cleaned out'. She also has little to no apetite but says she is hungry, however she will not eat. She now has hemmroids that will bleed both inside and outside the anus. She is such a loving little girl, but she always seems to be on edge and upset/uneasy about everything. I would love to hear what I can do to help her out! Thank you so very much!