Mental Health: Coming Off Mirtazapine

I currently write this, while battling depression and anxiety and coming off mirtazapine. The anxiety is a strange one that has started about a week ago, I just feel scared. Of everything. And nothing feels real. I know I am dissociating as I have done it before and will do so again, I know the medical jargon and that does give me some comfort, to know it is a symptom. Not a state of being I will be stuck in forever. But it doesn't stop the feeling and I feel like I need to be near people, near walls, enclosed. I feel scared of the wide world. I am currently withdrawing from taking mirtazapine which I have been on since 3rd February. It has not helped me at all. 
It is different to an SSRI, the more common anti-depressants, such as as sertraline and fluoxetine, both of which I have been on. It is different in that it is an atypical antidepressant. I have found it came with the following side effects:

• Severe weight gain and appetite increase (I gained a stone in a month!)
• Constipation
• Tiredness in the day (I have been like a zombie the day after taking it as I take it at night, I have been slurring my words, unable to keep my eyes open, sleeping too much!)

I have spoken to my Doctor and my Psychiatrist and they have both agreed I can come off of it. I haven't noticed my low mood or anxiety to have alleviated at all while on the medication so there doesn't seem much point in staying on it and becoming fatter and more zombie-like.

I am hoping they will replace it with a different anti-depressant as coming off of it my mood has decreased. I take it at night to help me sleep as I was on a helpful concoction of sertraline 150mg daily and quetiapine 150mg at night and this together fought my OCD, anxiety, mood swings and insomnia. But now it is all up in the air again as since being hospitalised and taken off sertraline completely and quetiapine at night due to overdosing on it and being seriously ill, to moving onto Depixol injection (flupentixol, anti-psychotic, for mood stability, anxiety and depression) and mirtazapine as the anti-depressant (instead of sertraline) and sleep aid (instead of quetiapine) and Depixol as an added mood stabiliser.

I am weary about what meds they may or may not put me on and just want to go back to sertraline and quetiapine as I was on them years and they were my comfort blanket. 

I write this experiencing dissociation and wanting to run back to my Dad's house and say "Cuddle me til this is over!"

I am going to try and read or do something. I need to take 15mg mirtazapine (the lowest dose, which is apparently the most sedating, weird I know!) instead of the 30mg I was on until Friday when I have a phone call booked in with my psychiatrist and he will talk me through what I will try next.

Wish me luck as I don't feel too good, my mood is low, my anxiety is high, if only they were the other way round.