Really bad headaches from..? please help?

my fiance has been getting these horrible headaches lately..behind the eyes..above his neck.. and directly ontop of his head..he has been slightly dizzy as well..we are confused as to what is causing these..its pretty much a constant headache..it doesnt go away..not even taking any sort of pain reliever..this is what i think..hes on lexapro for anxiety issues..hes been on it for under a year..i am wondering if he needs to up his dosage..or if his body just is trying to tell him he doesnt need it anymore..he also has just got a job as a firefighter and has a new love for caffeine which he never drank much of before..could this be a reason for sudden headaches? is the caffeine not mixing well with the lexapro? i just feel so helpless when i cant control his headache..any input is greatly appreciated..!