Re: low body temp, fatigue, insomnia indicates what
It could be many things. Get a thyroid panel run along with a blood chemistry panel run. Talk with your MD about adding ferritin, vit D, and vit B12 as well. Thyroid or dysfunctional blood chemistry can be at fault. Symptoms alone will only tell you something is wrong.. not what. Many things can be attributed to the symptoms you stated from poor diet, exercise, and sleep habits to thyroid dysfunction. So when in doubt get it checked out.
If we learn by our mistakes, I am working on one hell of an education.