Gaviscon but no sleep

Hey! My little boy is 6 weeks old.
He was cramping really bad, crying after feeds arching and climbing up me so I called the doctors and he put him on baby gaviscon to put in his milk (hipp organic)..
He was never sick. 
He's been on this now for 2 weeks, It made everything so much better, he wasn't crying after feeds and was getting his wind up fine but the past 3 4 days he's just crying all night, I have elevated his cot but he won't settle unless I hold him but still pulls his legs up on me and cries and whines but he isn't constipated, he's pooing 3 4 times a day which are soft and normal looking. In the day time now he's recently started being unsettled as soon as he's asleep and I put him down he screams then as soon as I pick him up he's okay again. 
I just don't know what to do, do I carry on with the gaviscon, do I try a special milk could it be lactose related.. I just don't know.. I'm so shattered and can't get anything done as he's always in my arms but ill do anything as long as he's settled and catching up on his sleep but really need something for a long term fix. Advice is grateful x