constant need to pee

Lately I feel the constant need to urinate. I went to see the doctor thinking it was an UTI even though I was not experiencing pain or burning. I was informed it was not an UTI. The sensation went away but three weeks later it is back. In the morning my urine has such a concentrated look and a foul odor. The only relief I get is if I am constantly drinking fluids and have a full bladder to release. Any ideas???