Blood in the urine can be a sign of an infection of the urinary tract—either the bladder or the kidney, but you are already on antibiotics for that. Assuming you are on the correct antibiotic (based on the “sensitivities” of the bacteria on urine culture) the bleeding should have stopped after a day or two. Beyond that, blood that is seen when urinating can come from the urinary tract, vagina, or rectum. Assuming it is really in the urine, the most likely cause is a kidney stone, which might also explain the pain you are experiencing.
It is worth remembering that your care provider can’t read your mind, and doesn’t know what happened after he or she gave you the antibiotic and sent you on your way. In order to sort this out, you need to call your doctor or midwife and report that your symptoms haven’t gotten better. Your team will need to see you, identify for sure where the blood originates, and evaluate the cause.
If you were earlier in pregnancy, the contractions would be more concerning, and would require an immediate call to the office, and probably a trip to the emergency department. Contractions, even strong ones, are not that worrisome at 35 weeks, because babies do pretty well if born within a month of the due date. Earlier, strong, or recurrent contractions or vaginal bleeding require urgent evaluation.
So take care of yourself, drink lots of fluids, and call your doctor or midwife to report the persistent bleeding and pain. You deserve a full evaluation and appropriate treatment, so you and your baby-to-be can stay healthy and pain free.