I had lots of trouble with DS after comp feeding him between the ages of 3months and 9 months.
DS would scream his heart out, go red in the face, cry, and cling to me as tightly as possible. It ws heartbreaking and noone wanted to help me. I knew there was something wrong, but everyone just kept telling me to do all the normal things.
I got fed up adn went to my GP who referred me to a Pead. The pead ws great but also a little baffled. We tried DS on a high fibre diet (lots of baked beans hommus etc) and also put him on soy formula to see if it was a cow's milk protein intollerance. Nothing worked, including adding probiotics to his food. I was so frustrated.
A good friend saw DS at his worst, and suggested something she did with her daughter. Vaalia yoghurt. I gave it a go, and what do you know, then next day DS soiled his nappy without screaming. From that day on, he has not had one single problem. His poos do get a little on the hard side on the odd occasion, but no bleeding, no screaming, no sweating etc etc etc.
Giving him Vaalia yoghurt was the best thing I ever did. I know it doesn't sound very conventional, but it's just an option for you to try if you want to.
I gave DS Vaalia most days for a good 2 weeks, and then every so often after that for a few months. He hasn't had Vaalia yoghurt in a good year now and we've still had no issues. I really believe it was all to do with the flora of his gut. I feel that if I didn't comp feed, he probably wouldn't have suffered for as long as he did.

Good luck with it all. I remember how heartbreaking it was and I hope you can get something that works.