Thanks for your concern.
I strongly advise you to take baby back to hospital immediately since increased white cell count, young age of the baby, sleepy / fussy baby & bulging soft spot strongly points to the possibility of infection of brain or its lining ( so called
meningitis /
encephalitis).
She should be admitted to hospital & need appropriate tests & treatment by antibiotic injections.
Please take this advice seriously.
I am also really concerned.