What Causes Bloating Above The Belly Button With Lower Back Ache?

started a diet back in september, lost 2 1/2 stone up to december. after christmas started being 'silly' with eating habits and often didnt eat a lot! got to the point i was on less than 1000 calories a day. lost another 1 1/2 stone but looked tired, was tired, lightheaded, couldnt sleep and stopped having periods. woke up to the problem beginning of april and started eating 3 meals a day and healthy snacks. body reacted fine to this and i started having more energy, sleeping better and periods came back. 2 weeks ago i started being bloated which got worse after i had eaten. the bloating was above my belly button. but now its below my belly button and my lower tummy is constantly rock hard. my lower back also aches. ive just had a urine test at the doctors and there were traces of blood found in it. im not due on till wednesday. i feel full alot of the time to! im a 33 yr old female, 5ft 10 and weigh 11stone 2lbs. any ideas??