Hi DeftRabbit
I just wanted to say i understand what you mean. I also have bipolar, and after a time of high stress 5yrs ago i developed an eating disorder after i wanted to lose 7lbs. The diet went crazy. I wasn't restricting as low as you are (mine was 800) and i went to my doctor for help. Essentially he told me it was because of anxiety and gave me an antidepressant. Then i self referred for NHS counselling (i think its about 6 sessions) and she never discussed it either.
The AD made my moods swing like mad which led to the bipolar diagnosis.

5yrs later and I've restricted the whole time. The number has gone up and down, and i managed to gradually regain the weight i lost minus the bit i wanted to lose in the first place.

In September i felt panicked about my weight again, but i still think maybe it's stress related due to my son's medical problems. It's a form of control when everything else feels out of control. It's the one thing i can 'achieve' and keep a grip of.
I also don't want to tell anyone about it because i don't want anyone to take it away from me.
I lost weight at first since Sept, but I'm not losing weight now despite the low calories, so i think I've probably screwed up my metabolism. Of course years down the line there can be medical problems because of what we are doing now. And i know that, but i still can't let go.

In the past i have fought through the thoughts and managed to increase gradually by myself, so it can be done. Sooner is better than later.
You can still feel like you have control at a much higher intake than 200cals, i know its hard to get past the number in your head, but i just kept trying and it was ok.

Having someone to talk to and support you would be more help than trying to do it alone.

Take care