ah i really feel for you - I have a similar issue but baby comes longer session - slightly older baby too but won't eat, won't settle for sleep. At first just cried constantly - I have had improvements and is settled now when i cuddle but only really happy and content if i hold / cuddle ALL THE TIME!! However, the baby was away last week and I have felt like a different person and realised its not just the baby that i don't seem to be able to give what it needs but the other children in the setting aren't having the focus and attention they deserve either. ALso I felt so relieved and realised how much anxiety i feel when child is coming that day!

Instead we had so much fun and did so many activities that i just haven't been able to do one handed with a fussy demanding baby! I've kept the mum up to date with progress but been honest about how difficult it is as a lone practitioner and how clingy and upset baby is! (She thinks its wonderful that he loves me so much and is so attached to me but I just think he is really insecure in general!) I have never had such a demanding baby and am thinking of giving notice even though it is well past the 4 week settling in (so i'd have to give 4 weeks notice)

Things i have tried that have helped are playing peek a boo so child gets used to not seeing you and then you are there, sitting with child on lap to play , then next to, then inching slowly a bit further away, (but then sometimes complete panic and crying - same as when child crawls away itself and suddenly realises its on other side of room!) also putting child in high chair to play so they can see you and everyone else but be independent (this has been most useful for this child) and just recently i have been trying delayed gratification - so when the baby instantly starts crying when i put them down i don' t pick them up straight away - this has been interesting because sometimes they stop as if they are thinking 'why am i even crying?' (doesnt always work!) However even with this small progress because child spits out food and won't settle to sleep i still have 2 -3 hours a day when child is inconsolably crying and is distraught / hungry / tired!
I probably should have given notice a really long time ago but have never had a child be so unsettled for so long and I think the parent is struggling and granny won't help becaue child is so difficult!

Fingers crossed for you xx