What Causes Pain In Abdomen With Painful Urination?

Hi I constantly suffer from what I think is cystitis. I have lower abdominal and back pain, have pain when urinating. I have been tested for uti but the test this time is negative though I have suffered from uti s on previous occasions already in the last year. I have been to the doctor and have had a scan to check my bladder and kidneys. The scan results came back fine; that I am emptying my bladders normally. This problem is starting to effect and take over my life. I used to an energetic and bubbly person, but im getting tired, tearful and disheartened that I cant seem to sort this daily problem out. I have a good healthy diet and drink plenty of water a day. I have the urgency to get up in the night too. I drink cranberry juice, take actimel every day. What advice do you have.