It is not OK for you to wear the old contact lenses. The contact lenses have their own expired time. You should use them within the expired time. If you use the old contact lenses, you may find the blurry vision which will cause the headaches right now. You should not wear the over expired contact lenses which may hurt your eyes because of the lack of water content and other elements. You should just change the new one with good water content to keep the eyes have the ability to breathe the new air. You should protect the eyes very much which are the most important part for the body.
Well, in my opinion, it is possible to have headache when you wear old contact lenses. As we know that after a long time you do not wear the contact lenses, it will just not be accustomed for your eyes to the old contact lenses. And at this moment, you may feel headache. Also, the old contact lenses can have many bacteria. And that may lead to eye infection to you. So you should not wear old contact lenses. or it will lead to many eye diseases.
Well, it seems that you are very interested in wearing contact lenses, which is quite good and make you free from those glasses frames. However, I should remind you that by wearing too much contact lenses , there would be some side effects not only on your eyes, but some other parts of your body. For example, you would feel dizzy, red eyes, itchy eyes, etc, and headaches is possible. So all you have to do is to take care of your eyes and pay attention to your eye health.