I had a perfect vision until I suddenly developed a double vision when I was on a Europe trip, doctors cannot diagnose what’s wrong with me?

I’m a 32 years old male from Sri Lanka. I had a perfect vision until I suddenly developed a double vision when i was on a Europe trip. This happened on the 17th of April 2017. I had a severe headache by around the 14th and I took paracetamol. I noticed a change of focus on my left eye sight corner with the headache. I rested well thinking this is for tiredness. On the 17th morning when I woke up I had developed double vision. I have to close one eye to have a clear vision. Checked with eye specialists in Paris and they said my eye pressure is normal and nothing wrong with the vision (as i could see clearly with one eye closed) and no change in structure. Within a week people started noticing a squint too. I came back to Sri Lanka only on the 1st of May. Consulted Neuro specialists and Eye specialists. They did many tests including MRI, sugar, thyroid, cholesterol, ANA, chest x Ray etc and all reports were normal. The eye pictures were also normal. Hess test showed that there is a problem with the focus and that there is quite a noticeable squint. As all reports are normal doctors cannot diagnose what’s wrong with me. They advised me to just stay like this and it will go off. I’m on medixone for the last two weeks. But I don’t see any improvement in my double vision condition or the squint. I get the headache too on and off. And my left eye vision is now slightly blurred. Please let me know doctor what this condition is and what treatment is available? Looking forward to hear from you as I’m really in a helpless situation with no hope here for a quick recovery.