I've had this happen....where I've gone to the doctor looking for reassurance and came home with even more fears! My allergist sent me to an ENT for something he saw in my nose that was "like nothing he had ever seen before". So I get nervous enough for that, go to ENT hoping to be reassured and he orders Cat scan! Ugh I was a mess waiting for results and someone to interpret.... It was nothing tho. And then a long while back when I was in the midst of worrying about MS I went to the eye doctor and confessed fully to HA and said I was afraid of MS and hoping for her to help me. It's the only time that I've talked about HA to a doctor and didn't downplay. Well don't you know she says "well, you have elongated something or others and we DO see that in MS patients." And she proceeds to ask me about other neurological symptoms and explains how MS is officially diagnosed. I was lucky I could drive home I was such a mess.
I am telling these stories only to show... I don't have MS. And whatever is in my nose is still there. But nothing's happened and it's been almost 3 years. The problem with HA is that it makes you interpret normal bodily functions in a terrible way. Then when you explain what's happening to a dr, they are kind of backed into a corner - they may firmly believe that there's nothing wrong. But if they don't know you, and they hear you say certain things, they are going to do some tests to follow through. They have to! But it doesn't mean anything is wrong.... Try to stay as busy as you can until the MRI. Accept that you won't be yourself until it's over and just pass the time. And when you get an all clear, get a plan going deal with your anxiety. But for right now now its not realistic to solve the anxiety piece of things. When you're right in the middle of the worst part of a scare, you can't see past it. None of us can! So just get busy for now and put one foot in front of the other for a while.