Suggest Treatment For Severe Headache

Hi im a 24 yr old female,ive sufferd with really bad headaches for a couple yrs,ive just changed drs,only seen her a few times,but my headaches have got alot worse the last few months,ive had many medeications that have not worked,im currently on job seekers allowance but now i really feel as though i cant work at the minute,would the dr give me a sick note for headaches?its the first time ive done anythin like this so dont know how it works,how do i go about asking for one? Thanx.