Can blood tests detect brain tumors? i had one a week ago and now i'm feeling pressure on head or headache. no other problems tho i'm 17 years old

Mixed antecedents: A week ago you had either a brain tumor or a blood test. I'll go with blood test. Now a week later you're feeling "pressure on head." Do you mean "detect" or "cause"? Either way, the answer is no. Even if a blood test somehow COULD cause a brain tumor, it would have to be an amazingly fast-growing tumor to cause symptoms after only a week. Also, you say you're 17 but your profile says 19. (?)