Pain in bladder and base of urethra.

Dear Doctor, I was having a kidney stone in my ureter last month and it passed away (6mm) after 10 days of medication (veltam). My doctor confirmed it in the kub scan. Now I am having pain in my bladder area and a sharp pain in the base of my urethra for last 2 weeks. Took CT scan and it came negative for any obstruction apart from a 11mm stone in right kidney(which I am having for 2 yrs),. Doctor said nothing to worry about the stone inside the kidney now. My culture report came as ecoli growth and taking nitrofurantoin tablet for 5days. No luck with that. Then taking faronem 200 tablet for last 4 days and still the pain is there. Having a pain after urination and sometimes a sharp pain on my left side of my urethra base. Pls. Help. I am loosing confidence sometimes on antibiotics. Thanks in advance.