Would a blood culture be positive if i had meningitis?

Not always: It depends on how bad the meningitis is, but it helps narrow down the antibiotis if the blood cultures were positive.

Maybe: For a blood culture to be positive you must catch the germ while it is in the blood. Doing so is not always possible, even when it spent some time in the bloodstream. To have meningitis, the germ must enter & reside in the layers of the meninges. It is often a final destination.