I agree with what Rachel said. I don't know about the 3 day course line - that's a newby to me!
Blood indicates there could be a uti but certainly doesn't mean you have one. It is important to do a midstream urine test and have it cultured. This will tell you what is going on and you will also know from this what AB's the infection is likely to respond to (if you have an infection).

Just going to your gp will suffice for all of this - it doesn't mean you need to see your obs. It is important to get things looked at though as UTI's are often asymptomatic and they can if left untreated be a cause of early labour.

I would certainly see your gp.

Good luck with it