Phildo2004. I have experienced something similar to what you are describing. This was only once but I'll get back to that. I felt as though my brain was swelling inside of my skull and it didn't have any room to grow. This occurred when I had a pretty serious concussion skateboarding and fractured my eye socket on a set of stairs.
Once I was describing the feeling of pressure and my friend said, "Oh, that what a migraine headache feels like to me." SO, this shows that some of the symptoms that make you feel like there might be a tumor or something could also be caused by something as minor as a headache.
I have sinuses, but certainly no anxiety linked to them. Also, I rarely get headaches but have had a few sinus headaches that portray a similar, though less intense, set of symptoms. Hope it works out. Oh yeah, try sleeping without a pillow. I DO have neck issues a lot of the time and sometimes that helps me discern what is causing the soreness. Trust your Doc until another one says otherwise. Take care and best wishes - Brett