Why are you "very scared"? Many, many people suffer from headaches and the vast amount of time, there is nothing seriously wrong with them other than the pain from the headache. If over the counter medicine hasn't helped you, see a doctor for help. Stop your suffering.
And many people also have pains in their knees and their back, especially with a reason that you mention above. Usually with no reason.
If this is the worst that you have to worry about, you are very fortunate.
Good luck.
my pains in knee and back.
I forgot to mention that the pains in my knee had stopped after I worked out because I had not worked out in ten days and I usually work out every other day.