Bladder Pain During Pregnancy: Causes & Relief

Question
I am 29, mother of 2, 18 weeks pregnant.  Recently I had my ultrasound, 3 days ago.  The next day I felt the frequent urgent need to urinate and bladder/vaginal burning.  I did not, however, have any burning with urination.  I went to the ER because I thought I had a bladder infection.  My urinalysis was clear and the additional vaginal swab was negative for any infection.  I have no odor or discharge. He thought maybe the baby presented pressure.  He treated me for presumptive UTI, prescribing Macrobid and Pyridium.  However, I do not want to take any meds while pregnant if I do not need to.  I cannot see my Dr. for 2 more days.  I also feel that my vagina burns and I continuosly push it up for comfort.  While examining myself I noticed a small bulge at the entrance of the vaginal oriface.  I don't know if this is related.  I did have a Gartner's Duct cyst removed 3 years ago.  My question is:  Could my bladder be "bruised"  from holding my urine for the ultrasound, and can the pain go away on its own?  Should I take the Macrobid even though my symptoms have not gotton worse, just remained the same?

Answer
It cannot hurt to take the Macrobid during pregnancy, because it may, indeed, be a urinary tract infection. The irritation that you feel may have been due to extension of the bladder in preparation for the sonogram. If there is any doubt as to whether you have a UTI or not, take a culture and sensitivity of your urine. It is better than a urinalysis and will definitively determine if it is an infection. (It takes 48 hours to get a result). Give it a little time to resolve on its own.