I'm a 16 year old female , saw i spitted out bright pink saliva , but it is normal now , had been dealing with headaches mostly due to my poor eyesight, may be feeling tired and loss of appetite. what is it? is it cancer , tumour , brain damage ?

No reasoned answer can be provided after reading the vague symptoms posted. Rare things rarely occur. This is likely a treatable issue or issues. Take a list of your problems/symptoms with a timeline to a scheduled visit with your doc. With this, further questions/an exam and tests, the answers are possible as well as a plan for treatment.

There is no way to diagnose anything without seeing you. An exam os needed to help with your problems. It sounds that if your eye sight were improved that the head aches may also get better.