Urinary track infection. Will i know?

Its been a month after my delivery..I suddenly started having severe pain while passing urine, which I dint have till now, then since 2 days my lower back to the left side and also the tummy at times is aching very badly...so badly that I am unable to sit and breastfeed. I got the urine test done and it said I hav ecoli infection . my doctor started giving antibiotic injection (gentamicin,)and painkiller. now the concern is 1. only if I take the painkiller the pain subsides a little if not it's horrible..Can I take so many painkillers? 2. I read it somewhere that these symptoms can be a cause of kidney infection.🙄😥😓 3. there might be gall bladder stones please help me out as I am confused with all this 4. Or is there a chance of placenta remains? If so how will I know ?