Hi. I’m sorry you are going through this, anxiety is the worst, and unless you suffer, you don’t know what it is like. Firstly I’d say, have you been to the doctors? There are tens, if not hundreds of reasons for severe headaches… please go to a doctor… believe me I get the anxiety in going/ making the appointment but they are there to help you… I’m not a expert by any means, but I’d suggest they’d probably want to check your blood pressure/ heart rate etc… but please don’t ignore it, while it probably isn’t a brain tumour, whatever it actually could worsen c while you’re worrying about it. 
sending you lots of positive thoughts and hopefully you have someone to talk to x