I would see the doc ASAP. Not trying to scare you, but I have heard of a connection between UTI and miscarriage (although you are too far along for a "m/c", I would still be afraid of other complications.) I went to the ER with a UTI in September and found out I had been pregnant (didn't know, since I was on b/c). My doc said the UTI *might* have contibuted to my m/c.
Better safe than sorry! Plus, UTIs are just no fun. Ugh!
I agree with the above comment - definitely could be a UTI, call your doctor and let them know what is going on.
burning when you pass water is a definite sign of a uti. some women are very prone to them in pregnancy. see your ob/dr and they will prescribe anti biotics to clear it up, it's nothing to worry about.