There are nerves and muscles that connect to your eyes and allow them to move around. If one is damaged, the eye can't look in that certain direction. This will lead to crossed eyes and double vision since the other eye can still move. So the eyes can't move together.
There are many causes of this. But with your medical history and age, there are four things that come to mind.
One is a cranial nerve palsy. This occurs with small vessel diseases (diabetes, high blood pressure, high cholesterol, hardening of arteries with aging). The circulation to the nerve is cut off and it suffers a temporary paralysis. This usually resolves in 8 weeks or so.
Second is a stroke to the brain stem. This is the area in your brain that controls eye movement.
Third is an acute thyroid attack. This causes the muscles to swell up and will limit the movement.
Finally, there is a condition called temporal arteritis that afflicts women in their 70's and 80's. This causes double vision and headaches. This can be detected by elevated ESR and CRP levels in the blood.
Finally, there is a condition called myasthenia gravis that is a neuromuscular disease. It can present as double vision or droopy eyelid.
You need an MRI scan of your brain and orbits to determine the cause. You also need some blood testing to evaluate for some of these conditions above.
Hope this helps and thank you.