Anyone else?

I'm about to be 28 weeks and since 22 weeks or so I have been experiencing extremely cloudy urine. Never seen it before in my life. It's not every day. Maybe once a week or a couple times. Sometimes not at all. But I've noticed the days I experience it I get bad back pain. Every time I've been tested my doctor says I don't have a uti but I've been told there is some bacteria in my urine. Doctor doesn't seem concerned I guess. Anyone else experience this and is it something to be concerned about?