Tenderness In Lower Back, Tiredness, Frequent Urge To Urinate, Lightheadedness, Vomiting. Urine Test Clear. Reason?

I have pain/tenderness extending down into my lower back, particularly to the right hand side. I m going to bathroom a lot and have to go immediately when I need to. I am extremely tired and am finding it difficult to work despite being well rested. I feel generally unwell, light headed at times. I went to the doctor about two weeks ago and took a course of antibiotics . The doctor said there was considerable blood in the urine but when she sent a sample away for tests it came back as clear of infection but there were some unconfirmed foreign bodies in the sample. I feel even worse than the first time I went to the doctor now. I seem to have been plaughed by one bug or another since September. I have picked up every vomiting bug and cold going. Literally when one clears another arrives days later.