It sounds like you should have a complete thyroid check. Being cold all the time is a symptom of thyroid problems. Make sure you go to a really knowledgeable doctor.
When i take my diet pills (oxyelite) i get like that idk why!
Maybe your case since you are over 40 it might be signs of menopause or a hormonal imbalance.
the first thing you need to rule out is a heart condition. feeling cold and back pain are compatible.
it also sounds like Neurological - Orthopedic .
chills, feeling cold are typical of spinal cord injury and even bad vascularization of the spine. Bad blood supply to the spinal cord. do you feel weak on the legs too?
do you have vascular problems?
your blood pressure?
Temperature regulation problems are often associated with a thyroid problem. Have you had your thyroid checked?