Anak, this really needs a doctor's attention right away, hindi ito pwedeng palampasin until Saturday, lalo na kung bumaba pa ang levels from Sept 2 to Sept 4. Please bring baby to the ER or call your pedia NOW para sa proper guidance, okay? Low sodium in babies can be serious and needs immediate checking, especially with the UTI on top of it.
I know you're frustrated with your current pedia, but for something like this, go to the nearest hospital or emergency clinic today rather than wait, you can always find a new doctor after baby's stable and you understand what's happening. Don't stress alone, mama. Get her checked now.