I've got a high maintenance no 3 baby, and I've struggled with him I have to admit.
He was fine for the first 5/6 weeks, but then reflux kicked in and he screamed practically the entire time he was awake. Poor thing was in agony with reflux, so being horizontal was no good at all. I got through it by using a sling (a lot!), tilting the cot up, co-sleeping (which I hadn't done with my previous 2) and also by keeping up the pressure on my GP to find some sort of solution to the reflux. First we tried Gaviscon, then Domperidone and Ranitidine to no avail. Eventually we got a referral to a Cons and got a prescription for Metaclopromide (sp?) which finally helped.
That was not until he was 17 weeks though, so we had ten weeks of hell. Unfortunately now (at 25 weeks) he's just started to get bad again and according to the Cons it's because he's rolling/trying to crawl. We're adjusting his meds and trying ot keep him upright as much as poss, but it's a case of riding it out until he's sitting most of the time and or walking...
If the Domperidone isn't working, please do go back as there are other drugs to try. Also try keeping them upright for half an hour after feeding and have everything on an incline rather than flat (even change mat!).
It's really hard, but my older 2 (aged 5 and 3) have learnt to be patient although it's been really hard at times. Also try to get people to give you a break, or give you time with your elder one. Naps slightly upright in the buggy might help too.
HTH a little, I do feel for you
x