lea, I had a UTI 2 weeks ago, really painful too. When I went to the loo, I had the urge to push like I was in labour, but had no stinging or burning. I went to the GP, who did a urine test, told me there were traces of blood and gave me some anti-bitotics. My back was hurting a little with it as well. The week before I had a sore back, around my kidney area, but we (DH and I) put it down to bub's position.
Maybe go and see a GP if you can, at least to put your mind at ease..

Nic