Recurrent uti? Is not getting reduced.

Hi doctor...two years before I had a 4.5 mm stone in my left kidney..then I had recurrent UTI..the stone got cleared off after taking medication..I had got myself treated for UTI by taking injections once in two months twice or thrice..then it seemed to reduce but again it started since one year..I have painful urination..when I drink lot of water it seems to reduce a little..but when my urine is concentrated I have pain while passing urine.i got urine culture and it came out that pus cells are 02-03 hpf...which means I don't have infection or infection is very less but even though I am drinking lots of water that pain is not getting reduced...I am very much worried about this problem..I think some tissue got ruptured near my urinary passage...kindly suggest