What could be the causes of having blood in eye discharge I have never had this before today and it has really frightened me?

Depends. There are multiple reasons why this can occur, infection, trauma, vascular malformation, etc.. You need to see an ophthalmologist who cam perform an exam to see what the correct diagnosis is.
Concerning! The cause of blood in the tear film must be discovered. It may be for a ruptured stye, but if it is spontaneous, source of the blood must be discovered! it could be a small abnormal blood vessel and it may be a tumor with abnormal blood vessels. No matter what, this should be seen by an ophthalmologist very urgently, before the source is masked!