i have a friend who's always complaining about terrible headache but when she saw a doctor and went through a blood check, he told her nothing is wrong with her. yet i need to mention here that her hair is so so thin that she's almost bald. is there a connection between the thin hair and brain cancer? she couldn't go for an x-ray since it would cost her a fortune.

No there is no relation beyween headache and thin hair

My guess just from hearing her symptoms would be hypothyroidism, which should have been included in her blood tests. I don't know where you live, but if I were she, I would simply go to the nearest emergency room the next time I had a headache. They have to treat you whether you can pay or not. Then she could work out a payment plan for whatever they do, but at least she'd be well.