I have an empty uterus, and my urine was negative. my last encounter was 8 weeks ago, so my question is did it matter if i didn't have an empty bladder?

Probably not: If I understand correctly, you did a urine pregnancy test that was negative, and that you had an ultrasound test that showed that there was no pregnancy in your uterus. If you had a vaginal ultrasound it does not matter if your bladder was full. Filling the bladder helps sometimes to see things on abdominal ultrasound. Usually pregnancy will be visible before 8 weeks either way.