You said he's on comfort milk, gsviscon etc, does he have reflux?
My DC2 was a screamer, all day, all night and then some! And I had a 22 month old too!
We tried every formula going, gaviscon, infacol etc. I felt like shit because all he did was cry, scream and puke everywhere. He was dropping centiles quite rapidly despite being 9lb10 st birth. I felt useless and often got to the point of crying myself because I didn't know what to do with him. No amount of walking him, driving him, cuddling him or anything settled him.
One day I let my guard down and a few tears escaped when he'd lost yet more weight at baby clinic. I told them exactly how awful it was and the midwife made an appointment to come and see me at home a few days later.
When she came we had a long discussion and on the back of it I made yet another Drs appointment for DC2, but this time I was determined to sort this out. I now had the confidence from speaking to the midwife that his constant screaming was not just a difficult baby and wasn't normal.
Finally a dr listened to my concerns and prescribed ranitidine. Alongside the gaviscon, this changed my life overnight. He went from unbearable to bearable. Don't get me wrong, it was still very hard, but not impossible! He began to gain weight and he didn't cry all the time. Their were moments of peace. Over the next few months, that increased as we settled into a routine and I got the dosage right for him.
I also was a bad mummy and let him tummy sleep (with an angel care movement mat!) as he actually slept for 2 hours solid as opposed to waking up crying every half an hour. Managing to get some sleep that was a major turning point too, for both of us.
At 10 months, suddenly it was all over! He stopped being sick, was instantly a happier baby and started to sleep through the night occasionally!
There is light at the end of the tunnel. It's just really hard to see when it's you in that horrible, dark place.
It will get better, I promise!