TTC need some input

Ok so my husband and I are TTC, we started really trying about 4 months ago. I recently went to the hospital for a bad bladder infection and the hospital automatically did a PT and they said it was negative. Technically the day I went to The ER was when I was supposed to start my P but I have yet seen her pesky face. What are the odds of the doctors test being wrong?  I was cramping terribly today but I'm not sure if it was me steal cramps or bladder cramps..