Holding your urine for a few hours without drinking much water, as you did, usually concentrates it enough to give a reliable reading. Testing at 330am after staying empty since midnight is close to a first morning sample, so a negative result here can generally be trusted.
Next Steps
If you tested very early after a missed period or possible conception, a faint line can still be missed at this stage. Repeat with first morning urine in 2 to 3 days if your period still hasn't started.
Health Tips
Please see a gynaecologist if your period doesn't come within the next week, so the cause can be checked properly.