Blurred vision in eye? Now feeling like a sty?!

I am a healthy 22yo female.

For about the last month or two my left eye has been feeling unusual. It feels as if it moves slowly, and sometimes is blurry. If I put my hand over my left eye, my vision in my right eye is strong. However when I put my hand over my right eye my vision appears blurred at the bottom, and then weak throughout the rest of my eye and I can't read things at a distance. The other week I was using binoculars and realised I was basically using my right eye, when I closed it I couldn't even see a thing out my left eye except for a few flickers of the surrounding and then it would go black.

I woke up this morning and my left eye felt bruised and itchy on the lower lid only in the outer corner. It sounds like a sty? I used to get many as a child, but haven't had any for years. I've washed all my makeup off and am applying hot compressions to my left eye.

I think I will book an appointment to see an optometrist or other eye specialist, but for the meantime can anyone offer me any advise as to what may be going on with my left eye?