hi, i have been feeling extremely tired for about last 6 months. can t do anything physical, even too long shower takes me out. i also have headaches, brain fog, dizziness, balance problems, hunger. i finally went to the doctor, she did basic blood tests. everything game back normal, just vitamin d levels were little low (34ng/mL). i wonder is that could be the reason that i have been feeling sick? and what would be the safe way to get my vit D levels back up?k