Chronic constipation in 10 months old baby

HELP!!!

My baby is 10 months old and have since started constipating when I introduced solid at 6 months. Not straight away but gradually. At one time, he didnt do a poo for 2 weeks in which I had to give him duphalax (like oral thing that i got from the chemist). It worked and I stopped it. He did poo everyday, not soft ones, big diameter ones (adult sizes), and he always grunts and cries. But I was telling myself, at least he does it daily. But things got worst. started bleeding (fresh blood) everytime he does poo, I think he tears down there when he poos. So went to padaetrician, which suggested going back to duphalax for 2 months to see how it goes. I started 3 weeks ago now and it seems to have lost the usefullness. Lately his poos are hard again and bleeding again, even after upping the dosage (from 5 ml, to 6 ml and currently on 7 ml as suggested). I am really worried about this. I feel helpless. Please help!!!! also to add, I have been restricting and elimating known constipating food. He is still breastfeeding with one formula feed per day. He eats a lot of fruits and not on meat yet as one time I started him on chicken and he got worst. I give him diluted juice daily. I even stopped giving him baby cereal as i think the iron might get him. But all seems to be not working. =(