What Causes Headache While Having Sinus Issues And Thoracic Outlet Syndrome?

I have been suffering from sinus issues for the last month and a half. I have allergies as well as GERD. I get severe sinus pain, pressure and headache at the back of my head when I have an attack . I notice the pain happens when I am experiencing an allergic reaction and acid reflux. burning sensation in my nose, water eyes, severe sinus pressure above eyes and prickly feeling headache at the top and back of my head, and post nasal drip. When this happe I ve been taking nexium, zyrtec d, sudafed, neti pot and just completed a course of antibiotics (z pack) I felt fine for a few days and now it s back, along with bad breath. Do you think the headache is coming from sinus issues? It s just a strange pain not really a headache just a quick stabbing pain/pressure. I also have issue with my neck (disc degeneration) and TOS (thoracic outlet syndrome) So at this point I am not sure if the strange ache at the back of my head is from sinusitis, neck or something else. Any advice