New, not sure where to post this. Basically, I intend on going to the doctor about this as soon as I have the time but would like some ideas on what this might be in the meantime.

I've had frequent headaches every day for two weeks. They're usually dull-moderate.
I get shivers and really bad chills after I eat. Warming back up again is nearly impossible for an hour or so. This has been a problem for over a year.
I have deep horizontal ripples in my fingernails and toenails. I don't bite my nails and have never significantly damaged them. It's in all of my nails. This has been slowly progressing for over a year.
My feet are almost always ice cold. This has been a problem for many years.
My hair is not as thick as it used to be-- seems to have thinned out.

I'm thinking this is a deficiency of some kind... but what? Or is it hypoglycemia? My family has a history of it. I'm 18, think I have a pretty good diet, take my vitamins, etc.