The normal armpit temperature is between 96.8 and 98.6 degrees Fahrenheit. Your temperature is low, but it may be caused by the thermometer you use. You can measure your underarm temperature multiple times with a mercury thermometer.
Also, hypotension often results in hypothermia due to insufficient blood supply. Hypotension can be seen in normal people, old people with poor constitution, hypothyroidism, post-operative trauma, heart failure, etc. Normal systolic blood pressure is between 90 and 139, and diastolic blood pressure is between 60 and 89. So, your blood pressure is low. But if you don't feel dizzy or fatigue, you don't need to worry too much. Generally, thin elderly people tend to have lower blood pressure. Sometimes, the incorrect use of a sphygmomanometer may make the measured blood pressure low. That blood pressure is not necessarily your real blood pressure. Hence, you should monitor your blood pressure multiple times or by ambulatory blood pressure monitoring.
At the same time, you can take high-quality protein, eat more fruits and vegetables, exercise properly to raise your blood pressure. If you feel dizzy, palpitation, etc., you need to go to a cardiology clinic immediately.