Welcome to the forum Nicola. Glad you found us but sorry that you are having this pain. Have you seen any specialists to rule out anything, such as ENT, neurologist, orthodontist to rule out tmj. Those are just a few to get you started.
Let us know how you are making out. i can add more as time goes on as i have been suffering with constant headache for twelve years and have done much investigations etc.
Take care
Suzane