Constipated baby

It breaks my heart that my DD has.had so many complications since birth(nothing major thank god, and knock on wood) but from birth had trouble regulating her body temperature. Was in the NICU twice. A couple of scary high fevers, milk protein allergy when we tried introducing milk at 1 year old. Started losing weight 11 months - 13 months old(supply dropped because I found out Im pregnant with my 3rd) Eczema rashes, 4 additional allergies. I had to be taught how to use an epipen. Weve been to the ER at least 3 times for allergic reaction. Shes now been pretty constipated for the last 2 months, slowly and progressively getting worse. We finally got prescribed lactulose, and a suppository. Today though was awful. Had to wait for dad to bring home the meds on his way home from work. She had already tried going 2 or 3 times and it retreated back in leaving tire tracks in her diaper. As soon as I gave her the first dose of lactulose, I inserted the suppository. As I was administering it she started pooping. The longest, biggest poop ive seen to date. The screams, the cries, just broke me. Ive been telling her pediatrician about it for 2 months and they literally say "add more juice to her diet" well she doesnt take it on her own so I have to give her whatever she would take down with a medicine syringe. Wasnt ever close to 10ml. I dont see why it took so long to get the help she needed. We were following up with GI after her weight loss and while shes finally gained some weight I discussed the constipation issues. At first he didnt want to prescribe a suppository, but then at the end of the appt he witnessed what pooping was like for her. I told him she often ends up straining so hard im worried shell get hemorrhoids, and her anal sphincter is constantly tearing because of it. As she was straining he finally was like "suppository is definitely needed in a case like this" so were hoping to get her regulated then possibly slowly wean her off the Lactulose. Im so happy we have help now but its upsetting it took this lomg for them to help. I only ever want whats best for her, its not like Im pushing them to give her unnecessary meds. Rant aside, I just wish doctors would listen to parents a bit more and understand every concern should be taken seriously but also investigated.