I had my first admission to hospital with pyelonephritis at about 30 weeks, am now 36 weeks and still in pain - the infection is under control thanks to antibiotics (first drip, then 3 week long full oral courses, now on maintenance antobiosis), but I have developed hydronephrosis - basically one of my ureters (the tube from the kidney to my bladder) is blocked a little bit, probably because of the uterus pressing onto it) so urine is held back in the kidney a bit, causing swelling, dilatating of the ureter, which is painful.
When the infection was first present, the pain was permanent, now the stronger pain comes in attacks, mostly in the evenings. I've basically have been in pain for the best part of 6 weeks, and don't expect it to get better until the baby is delivered.
There is the option of a ureteral stent, which isn't as easy to place in pregnant patients as it is in non-pregnant ones, and comes with its own risks, so currently I'm bearing it with the help of painkillers when I can't cope at all, to avoid this.
Will discuss options with obstetrician again next week, being followed up regularly, have racked up 11 sick days because of this in the space of 4 weeks, 2 hospital stays, and numerous visits to the triage unit.
Sorry to not have a more cheerful story.
Being doubled up in pain is certainly not good, and antibiosis should kick in quickly, if the bug is sensitive to it - I went from being very ill (chills, fever, vomiting, bug could be isolated in my blood) to feeling ok-ish within hours, just after two IV doses. Have they done a culture of your urine to see whether it is suspectible to the antibiotic you have been subscribed?
If this is not getting better and the pain is not subsiding, I would not wait until monday.