I don't know what is wrong with my eyes

My right vision is perfect, I have nothing to complain about it. But when I block my right eye my left eye gets blurry. But it turns out that I can accomodate my vision so that I can see normally with my left eye as well, but when I do that I get double vision and my right eye gets blurry instead. But when I go to the doctor, they say there's nothing wrong with me. They say I don't need glasses, since I can see well with both eyes. But I have tested glasses with hyperopia correction only in the left eye and they allow me to have a good vision with both eyes at the same time, even though I can see well with each eye alone. So, what is wrong with my eyes?