My menstrual cycle is 25 days late. At 10 days late I did a blood test at the doc office and it was negative.. still having symptoms.. what could this be?

Might still be a pregnancy that just wasn't picked up early, but it could just as likely be you are going to skip a period. This sometimes happens, even if it has never happened before.
If you still have pregnancy symptoms, I would try another test. Otherwise, wait until next month and see what happens with your period.