how old are you? my dad has a very similar condition. He says his ears ring all the time, but he's 70. Maybe there's something making a high pitched noise in your normal resting area? if you leave an old tv on without the cable is can generate a high-pitch sqeual from the static. But seriously: You said it wasa serious health question, right? So see a doctor then. Don't ask random peeps on the internet for a diagnosis.
Sometimes it can indicate your wellbeing is getting marginal, that you are run down, possibly will feel light headed too or that you have a cold or flu-like condition even possibly glue-ear (easily checked and treated)
Check you are eating all food groups getting proper sleep and getting "heart pumping" exercise or sport.