Hello and thanks for trusting me to help you. I am a board certified consultant with over 30 years of experience.
Well persistent sharp pain shouldn't be ignored as you had already tried Advil and heating pad.
X-Ray/MRI of Lumbo-Sacral Spine may be done to rule out lumbar radiculopathy/prolapsed disc.
Ultrasound of whole abdomen to rule out kidney stone.
Urine complete examination to rule out urinary tract infection.
But since the pain is sharp on standing it is most likely due to pinched nerve.
You should hydrate yourself with plenty of fluids.
Also your doctor may prescribe you strong pain killers orally or injections.
I would recommend to see your doctor or visit ER ASAP.
I hope this helps.
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