Welcome to the site.
I am Dr. Kaushik and i am a psychiatrist and i believe i can help you with your problem.
Well you see the flat mood that you are struggling with as of now is a part of Bipolar
depression aka depressive phase which is usually episodic in occurrence lasting several weeks to months in a Bipolar 1 or Bipolar 2 patient before a switch to either normalcy or hypomanic or manic episode shall take place.
I can understand the limitation of not using anti depressant or mood elevating drugs like modafinil in your condition as they may precipitate manic/ hypomanic episode thereby compromising your treatment so with this sort of restriction with the drug use to counter this depressive phase you can try some supplements such as Omega 3 fatty acids or Ginkgo biloba or combination of both to help passing this phase which is going to self limit or resolve itself in due time as is typically seen in bipolar disorder.
Other than trying supplements and patiently waiting to come out of the depressive phase one other very effective treatment option is available and that is called as TMS therapy that is Transcranial Magnetic Stimulation therapy which is a non-invasive treatment modality basically used to treat clinical depression but it can very well be applied in your case since drugs like anti depressants are not an option and it shall help you to overcome this depressive cognition.
In this TMS therapy an electromagnetic field is created over the head via TMS machine which then is used to stimulate areas of brain so as to treat depression.
I am sending below a link which you can go through to know more about TMS.
So to summarize if you can combine the present drug regime + omega fatty acids and ginkgo biloba + CBT + TMS therapy then you may find effective and faster remedy for your depressive cognition.
I hope this helps.
Wish you all the best.
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