In January of this year something happened to me and I changed. 
I felt a sudden and dramatic shift in my personality and the way I felt in myself. I have never ever experienced anything like this before. 
It started in January with a persistent feeling of dread, everything felt grey, I had a weird feeling of brain fog, and I was convinced something was really wrong with me and I was going to die. I went to hospital where they didn't do any tests, but said I was having a panic attack and sent me home.
however, reading about panic attacks I don't feel like this quite fits how I'm feeling. 
Around this time I also developed insane insomnia, so I couldn't sleep at all for over week (I've never had insomnia before) and I also lost the ability to tell if I was too hot or cold. So when I was explaining how I felt to my husband I said that I was awake all night shivering, and my jaw was quivering as if I was cold, but I insisted I wasn't cold, but that night I put an extra throw on my bed and warmer pyjamas for bed and that night I managed to sleep. I've always thought this was really strange, because I was clearly very cold but I could not feel it or process it. 
This strange feeling of being taken over and not being myself seems to come and go. At the moment it has become really bad and it there about 90% of the time, but suddenly it will disappear, and it is as if all the brain fog and strange symptoms completely disappear and suddenly I am 'back'. The relief is amazing because suddenly I feel 'normal' again, but then just as suddenly I can feel a sudden shift in the atmosphere and within myself and it is as if I am gone again. 
I have had strange things happen suddenly, like my neck is really giving me problems a lot at the moment and I am often in pain with it, I get a lot of headaches although I've never been the sort of person to get headaches and I get weird flashbacks to old memories for seemingly no reason.

There is something inside me that is telling me this is really not normal and this is more than some sort of 'anxiety' - plus I have nothing to be anxious about! It makes no sense for this to appear out of the blue. I feel like I want to tell the doctor I would like an MRI. Can I just request an MRI? I don't want to waste anyones time, but I really feel like something is wrong. 
can anyone relate to this? Or offer any advice? I'd really appreciate it.

If you managed to get through all of this then thank you