i've replied to a few of your threads in the past because our symptoms are literally exactly the same. i too get the symptoms even when i'm not feeling anxious, so i always get frustrated when someone else passes it off as "oh you're probably just having a panic attack" or something along those lines. it's like, no, i know what having a panic attack feels like, i'm definitely not having one while just sitting on the couch reading a book! like you said, the symptoms crop up no matter what we're doing. but we have to remember that even when we don't feel PHYSICALLY anxious, there's always that lingering anxiety in the back of our head that can still cause physical symptoms; when we exhaust our brains with constantly worrying, even minor worrying without panic attacks, we're not letting our body calm down enough to let the symptoms subside. if our brains had a gauge, we'd always sort of be tipping near the very top of it because our minds are so USED to worrying about something, if that makes sense. so even when we're not feeling physically anxious, our brains think we are, which can explain the lingering, chronic symptoms we experience.
anxiety aside, though, your symptoms could also easily be attributed to something inner-ear or sinus related. i know how scary these symptoms are. my biggest fear in the world is a brain tumor as well, so you're not alone. but since our symptoms are so vague and all over the place, they could easily be something much less serious and very benign. i know it's easier said than done to believe that we're okay when we're so scared of a certain disease, but it's just something to think about. there's always a more common, less serious cause for the symptoms we're feeling than the Big Bad Disease we're obsessed with.
edit: even as i type this, i'm having a headache and sore/heavy eyes with pressure behind and around them. my head also feels super heavy and it's hard to concentrate. but sometimes you have to just ignore the symptoms and pass them off as nothing, no matter how worried you are. that whole "fake it till you make it" can really come in handy when it comes to getting over health anxiety.