Trouble urinating may be stress incontinence (urinary dribbling or wetting when you cough), urinary urgency (sudden urge to go to the bathroom and may wet yourself if you can not get there in time, this is commonly associated with pain), urinary incontinence (no or little control over urinating resulting in peeing your pants) and urinary retention (unable to start to urinate, bladder fills with urine and may cause abdominal discomfort).
Back pain and problems urinating can be a surgical emergency called cauda equina syndrome. This may be associated is numbness in the perineum (butt and groin), leg weakness, numbness or pain (such as Sciatica), urinary retention (unable to pee), urinary incontinence ( unable to control your peeing causing you to wet your pants) and bowel incontinence (uncontrolled bowel movements). If you develop these symptoms you should immediately go to the emergency room. You may have herniated disk (or something else) pinching your nerves that innervate your bladder and may need emergency surgery to remove it. Good Luck!