Unfortunately, most people are totally unaware if they grind their teeth. Only very few people can tell they do it. In some cases, family members are able to tell you if they hear it while you are asleep.
One sign is tenderness in the muscles of the jaw. Nocturnal grinding is like an 8-hour gym work out. Imagine doing bicep curls for 8 hours! How would your arm muscles feel and look? Probably large and sore! In the case of our jaws, our muscles can become very sore and create headaches.
It is often the case that people that grind their teeth also have other sleep disorders so specialised sleep studies may be required. If you also are a snorer and have sleep apnoea you could possibly grind.
The commonest sign of grinding is premature wear on teeth. Often this is seen in the form of chipping on the front teeth.
It may take a while for the thin enamel coat of the teeth to wear away but as soon as the softer dentine is exposed, the tooth will wear very quickly and may be noticeable to yourself or family and friends. Teeth may also look very small and a good comparison can be made by looking at old photos.