Doctors can be questionable people at times. Should add, not all doctors are like that. In my opinion, it can't hurt to do a scan, just to rule out anything that may need attention. A good doctor will put your mind at ease. A good doctor will wonder about a variety of possibilities. A good doctor is happy to rule out anything serious.
Personally, I'm not a medical person but I am sensitive enough to feel blood pressure and sinus pressure changes in my head and they definitely feel weird. I used to get 'Silent migranes' with some pretty bizarre side effects. While my regular doctor (who I no longer see) insisted I was experiencing anxiety and panic attacks and wanted to put me on medication, I wouldn't stand for it. I had to know what was really going on with my brain, why it was doing what it was doing. Another GP sent me for an MRI scan. It was a miracle, I was experiencing one of these migranes while in the machine. The timing was incredible.
Sounds like it could be sinus related, based on the fluid factor. Could also be tension related. Who knows. One thing you do know is that you're entitled to have anything serious ruled out, if you're that concerned. If you're happy to pay for a scan and there's no good reason as to why a doctor won't send you for one, perhaps consider finding a GP who'll order a scan for you. An open minded GP is the best one to have in my opinion, based on my own experience. You could always consider asking for the scan as a way of helping you manage your growing overwhelming stress.
Hope someone's able to put your mind at ease and give you the answers you need :)