I experienced sudden coughing up lots of blood, but i don't have bad cough and fever before it happened. what would be its cause?

This can come from a variety of reasons but needs to be checked immediately By a physician or healthcare worker

Please proceed to the Emergency Department. The source of bleeding may be your lungs or upper airway. Avoid NSAIDs and Tylenol. The evaluation should also include a chest x Ray, blood count and coagulation studies.

Fully agree with my colleagues, as this is indeed an emergency situation and intervention should not be delayed. The source of bleeding needs identification, and appropriate intervention now.