A temperature sensitivity warrants to look for thyroid dysfunctions. You can speak to your GP to order for thyroid function tests (T3, T4, TSH). Read the symptoms of hypothyroidism (under activity of thyroids);
Another possibility for these symptoms is some low grade infection. Again a blood work up, like blood counts ESR, urine examination, etc would be needed to establish that.
Hope this helps. Your follow up questions are welcome.