Can Dizziness, Headache And Nausea Indicate Brain Tumor?

Question: Back in early December, I was away for a week, and on the last day, I had a couple of very brief (like a second or two) dizzy spells. For about a week or two after that, I had what felt like occasional wooziness or unsteadiness, and some headaches. I called my doctor, who suggested I go to an ENT doctor, which I did. They did a bunch of hearing and balance/coordination tests, and everything was fine, but he suggested I have a Brain/IAC MRI, if it didn't entirely end by the New Year. 

I've still been having the occasional woozy feeling (not spinning, but a feeling of unsteadiness) from time to time, so I made the MRI appointment for next week. I've had very few of the dizzy spells (although I had one this morning) and the headaches have been much less (I actually have more neck pain than head pain, usually) although I have felt nauseated the last couple of days. I've had bad post-nasal drip/cough and thought the nausea could be due to that, or, maybe due to anxiety after making the MRI appointment (since it started a few hours after I made the appointment). 

Anyway, I suffer pretty badly with anxiety, particularly health anxiety. I guess I am aware that all my many, many symptoms can be caused by anxiety, and I think that that is what my doctor, therapist, spouse, and co-workers think is happening to me. But it is scary to feel headaches, dizziness and nausea. I am, of course, worried about a tumor or some other dire finding. To make things more complicated, I am supposed to fly to Las Vegas tomorrow for the long weekend. So I am also anxious about being away like this. 

So... do you have any advice? Would you advise against the trip? Is there anything you can suggest, or reasons you can give that I should not worry about brain tumors (I know they are rare)? I know you can't diagnose me over email, and there's probably not much that can be done until the scan. I am scared to take the Xanax I have (they may have expired a few months ago anyway) but I wonder if that might help a bit. If it is all due to anxiety (which is quite possible) I am so frustrated that I can't just get out of it.