Perhaps having your hormone, thyroid checked and adrenal functions would get you started. You endocrine system affects metabolism, mental state, digestion, body temperature and so much more.
I had a half of my thyroid removed 2 months after my twins were born (large thyroid nodule) and I have gone on a roller coaster ride of problems since. Unfortunately, I have yet to find a doctor to get to the root cause. Last August I had intense problems like you are having and the darkness of skin and my doctor insisted I should be on an anti-depressant. I was not depressed! I felt crazy, but it was like looking at through a clear window and not being able to do anything. Starting birth control helped immensely, but it is a band aid. In addition, there was a lot gong on then. My boys were 19 months, I weaned them, they were becoming very independent, they transferred to toddler beds and it was way too hot to get outside like we normally did. I think sometimes maybe there was too much going on, but I still believe there is more to it. Birth control helps with most of it and now I am terrified to get off the pill because I fear returning to that state.
I look forward to looking into bio-identical hormones.
I hope that you find the help and the peace you need.