Oh I am so sorry to read that you are going through this. I have bipolar and my DH is my advocate when I don't feel strong enough to put up a fight or when I am not sure of my behaviour. Your husband can absolutely help you request the change in psychiatrist and push it through for you - is he down as your main carer (for want of a better expression)?
You need a doctor you can trust which is half the battle. I am currently pg and at 7 weeks had a horrendous psychotic episode after a terrible time with a useless gynaecologist who didn't understand my condition. DH put in an official complaint to the hospital and fortunately my care was transferred elsewhere.
When I started lithium it was life changing in such a positive way. We have different conditions I know, but to get the medication sorted will be such a weight off your mind. My advice would be don't worry about weight. Get your mind into a healthy place first. You are definitely on the wrong medication.
Make a plan of action with DH as to what your next steps are and what you want out of your appointments. I always make a list of things to talk about so I don't forget.
Your gp can help push for a change in psychiatrist too. They are always there if you need to speak to someone. Do you trust your gp?
It must be hard but do try and be open with your DH. He sounds very supportive, non judgemental and will help talk you away from the voices. I know those voices all too well and it took time - but I tell DH now everything and he helps me realise it is OK. You are a good mum and you won't hurt your children.
My final point is absolutely yes to addressing the psychological aspects of what you have. I had intensive psychotherapy which was amazingly beneficial (I have borderline personality disorder traits). Talking therapy is really effective and a completely safe place to explore your anxieties and previous traumatic experiences. You are very right when you say it's not just a medical condition but a psychological one as well.
I do hope you are feeling better by now.