My yellow lab is sick. eye gunk/weakness/trouble eating?

Over the past few weeks my dog has been forming eye-boogers over the coarse of the day.we get them out, but over time she has been losing her appetite , which has been causing weakness. she will not eat any dog food i bring home.(but she did eat a McChicken from mcdonalds that i brought home today.) Anyway, i am wondering what this may be, and if there are any home remedies. if not, i am going to have to schedule a vet visit. i dont have much money, so i hope it wont be expensive! any help is appreciated!