Hi, I'm 19 And For About A Year I've Been

Hi, I'm 19 and for about a year I've been experiencing extreme coldness, my heart rate is always between 40-50, and I feel like being sick when I exercise. I've been tested for hypothyroidism but it came back negative but I'm slightly anaemic so I've been given iron tablets which has helped my coldness. Recently I've noticed that my fingernails are blue instead of pink, what could be causing all of this?