Dos having the fluid in your brain testd hurt ?? plzzz awnser !!?

im 13 my mum told me i have to have a bunch of tests done and one might be having the natural fluid around the brain tested in 2 weeks Ouch !! they stick a needle at the back off your head . the blood test dint hurt and neither dos injections but the lumber puncture ( the same thing but in your spine ) hurt so im rely nervous and know i shouldn't be !! help !!