What Causes Blood Taste In Mouth?

Hi, I was just sitting down using my computer when all of a sudden I tasted blood in my mouth, thus, I went to spit the blood out. I saw that it wasn t mixed up with mucus and that it was just blood but as I was trying to spit it out repetitively to work out where it came from, it started to diminish. I know it came from the upper respiratory system rather than from the lower as I did not cough it up or anything. I also did not have any blood in my nose unusually, thus, I am really worried it might of come from my brain. Soon after, I started feeling dizzy, weak and a headache, so I went to lie down for a couple of hours which then got rid of most of the pain. But when I woke up to use the internet, I m starting to feel the symptoms lightly again. I would very much appreciate any helpful response or opinions on this matter. Please ask me questions to further clarify the problem if it is still unclear.