What Is The Cause For Painful Swelling And Black Line In My Eye Wiyh Blurred Vision?

I have suffered for years with sore eyes and have seen several specialists. Some say it is allergies whilst others think it could be eczema related but I have noticed recently on the inside of my lower left eyelid a black line that runs the same way as my eyelashes and this eye is really playing me up it constantly feels dry and irritated and every few days it is swelling it is quite painful very annoying and very sensitive to light I am also getting a lot of string like discharge which I believe is my inner eyelids shedding and I am suffering alot of blurred vision any advice would be great fully received