Been there Oliv, and I would be right where you are now if it would give you a break.
Tried everything on my son... everything that has been mentioned - everyone swears by something different don't they, and because our babies are all individuals something different always works! My son LOVED osteopathy, but it didn't cure his colic... colief made him worse and infacol helped the most. The biggest and best cure was... hate to say it... time.
Otto no longer screams each and every time he farts, and I no longer need to walk round with him on my shoulder like a litle hairpin (found this to be a great position - massaged his lil tum and I could still get on with stuff if needed). The baby sling does quite good on the tum massage front also - but you can't sit down.. send your bloke or your friend out with him strapped in it. Tiger in the tree if great also, but it is all "hands on stuff" all the time. If you hold him and jiggle him (in pushchair movement mode) this may also help. You could also try "the pushchair", but at least 1 in every 24 hours I used to like actually sitting down myself
Wait for the 6 speed graco swing recommendations to come in - we call ours "the baby scarer" but it may work on your son.
Quick (and loaded!) question... does your baby feed a lot? My little un used to have loads of bottles a day, but they were just snacks to relieve his hurting tummy it turned out (yes yes, I know, I'm still waiting for the manual to come out..) A friend availed me of this, and it worked for my little individual - for her to get him to sleep instead of me feeding him and we never looked back.. (well, not often!)
I do remember at 3 weeks thinking that 3 months would never come.. it does, and quicker than you think, and you will really really really appreciate your little bundle.