Is your son perhaps having "night terrors" or night mares? (look it up online... these are 2 different night time issues... and it occurs at certain ages, being a developmental phase.) When they have these, they DO wake up screaming... they are scared. Night Terrors... is developmental.. and you can't really make it go away... it is a phase and will subside on it's own. But just read about it, to understand it.
Both my kids went through this. It's normal, though not pleasant, for them either.
the "excuses" are not excuses... these ARE things that abrupt a child's sleep. Your son is not doing it on purpose... he seems genuinely distressed. I know it's not easy... but your son seems to be waking for a reason... not just for the heck of it. It's not easy for him either... for a child, these wakings are just as h*** o* them, as it is on the Parent.
I would really ask your Doctor for any other advice. Is he perhaps having reflux? Stomach problems? gas? teething? Hunger (12 months is a growth spurt time), Night mares (which does occur at this age)? AND he's been sick a lot lately.... his body is probably STILL recovering. Or it's still bothering him. Have you tried teething tabs, like Hyland's?
Once, my friend's baby was always crying and screaming... she took her baby to the Doctor, who looked over her baby from head to toe, very closely to examine her. It was found, that a tiny blond hair was wrapped around her toe, and cutting into the skin as it got tangled tighter... it was barely visible to the eye. But once removed, the baby was much better. THIS was what was causing great discomfort in her baby. The point is... there is usually a reason WHY a baby is behaving this way... it is not just to be annoying.
I don't have any answers... sorry.
All the best,
Susan