Fiona, I had a UTI about a month or so ago, and I didn't have any of the burning/stinging that you would normally have with an infection. I had the awful urge to push everytime I went to the loo.
When I finally got to the GP, they said my urine was cloudy and had traces of blood (that I couldn't see) and that I had an infection
They gave me amoxil and GP also suggested that I take Ural as well. I've never had Ural before, and it made me feel horribly ill, so I only had the one dose of it.

In all honesty I didn't think it was an infection because I didn't have the burning/stinging sensation. I also drank a heap of cranberry juice before I got to the GP.
I would try to get onto your midwife and see what she thinks just in case it turns out to be an infection. You don't want it getting worse.

Hope all is well either way.

Nic