There are some tests that are able to detect pregnancy up to 5 days prior to your missed
period, but I always recommed waiting until you miss a
period .
Next, if the pain persists, you should get checked out by your doctor. It could be something like a urinary tract infection and you would want to have this treated sooner rather than later if it is.
Finally, if the consitpation/ diarrhea continues, you should ask your doctor about this.