headache dizzness felling like im going to pass out for the last two and a half years.

for the last two and a half years i've been suffering with headaches dizzness and feeling like im going to pass out. ive had all the blood tests done you can think of and apart from low vitamin d and b12 which im taking meds for everything else came back clear.also i was sent to see a nurologist and he asked me lots of questions and checked my eyes and pressed my head and said i was suffering with tension headaches. but the headaches continued so i went back to my doctors yesterday and she is sending me back to see the neurologist but she said she still thinks im suffering with tension headaches so why send me back im so scared it is something serious can anybody help.many thanks