There are many different causes of these kinds of symptoms. By far the most common cause would be some type of viral illness, such as the flu or the common cold. Viral illness in general tend to cause these achy symptoms because of certain chemicals that the body's immune system releases while fighting off the virus.
That being said, anemia can also cause similar symptoms, especially a feeling of extreme fatigue and also feeling cold, as can other conditions like hypothyroidism.
It is important to get these symptoms checked out. You could start by seeing your primary care doctor
, who can perform an examination and determine whether blood tests for anemia or other conditions are needed.
If the symptoms have just come on recently, they are more likely to be from a virus or other infection and less likely to be from a more chronic problem like anemia. However, regardless, if you have a high fever
, if you have trouble keeping down liquids, or if you have a severe headache
, you should go see your doctor regardless to make sure that no further treatment is needed.
I hope you are feeling better soon!