I have low body temperature too, almost always under 36 degrees. Makes it hard since most people won't believe that to me 37 degrees IS fever, not just mild temperature (including most doctors, who imho should know better.) It got a bit higher when I gained weight but not much. And I went from severely underweight to a slightly overweight, so it was a significant increase too.
I also have trouble sleeping and often feel totally lethargic so sounds a bit same that your problems
Part of it I can attribute to bad lifestyle but I'm also naturally a bit insomniac, I've had trouble sleeping since I was a child. For example I woke up 3am last night and the night before that I couldn't get sleep at all. It just seems to be something that doctors aren't willing to look in to. Maybe I ought to complain more. I've been eating the sleeping pills that they always prescribe for when I absolutely need to shut my eyes for 6-8 hours, but it's not real sleep. You wake up tired and your mouth tastes like a garbage dump ._. But eyes are rested. That's... almost positive. I've also tried melatonin but it really only helps to keep up an already achieved sleep cycle for a few weeks longer.
But one thing I found that once I do fall asleep helps me to stay asleep is earplugs. Damnit, I didn't know sleep until I started to use them. It seems that among other things I'm extremy sensitive to noise and it isn't something I had realized before.
But yeah, no help on the temperature side
