I Have One Eye(my Left One) That Tears Constantly During

I have one eye(my left one) that tears constantly during the day. It has such big tears in it, it encumbers my sight. What is going on with my eye? It starts early each morning, both of my eyes are fine and then I put my sunblock on being careful NOT to get it close to my eyes and then my left eye starts to tear and continues to have big tears in it all day that run down my cheek.