As you are getting close to 40 years of age, you are likely to have developed a condition called presbyopia in which it becomes difficult to see near objects. However, if you move them further away they can be seen clearly. It can easily be corrected with glasses. This can cause headache too. Other possibilities could be a refractive error or squint. You need to see an ophthalmologist/optometrist. Thanks.
O.K. then you need to get an orthoptic check-up done as well to see if thereis any squint or not. Other possibilities could be migraine, cluster headache or even glaucoma. For the first 2 conditions you need to see a neurologist and for the third an ophthalmologist. Thanks.
When the two eyes are not alligned in the same direction, it is called squint in simple terms. It can be of many types. Since, your eye muscles were underdeveloped, it is possible that you may have some residual squint. Thanks.