Go have your thyroid checked. It is a symptom of thryoid problems. I have hashimoto disease,where my body produces antibodies that attacks my thyroid, so I have an under active thryoid. My body temp is anywhere from 96-98. There are alot of us woman walking around with thryoid problems and doctors say there is nothing wrong with us. What other symptoms are you having besides feeling achy? It's worth a check. Go to the thyroid and thyroid support forum. You'll find out lot there and they are all very helpful and understanding.
My temperature tends to run in the 96 degree range in the first half of my montly cycle. Women have different ranges for what is normal for them, so I wouldn't worry.
Your temperature is fairly normal, maybe a bit low but I wouldnt' worry too much. If you haven't ovulated yet this month, that could be why your temp is low. or it could be for a number of reasons......probably nothing to worry about!