Any at home help for my cat? She is 2 years old and is quite small (she was the runt)?

my cat jumped out of the car a little ways away from our house and was missing for 2 weeks. She is finally home but she is very very thin and extremely lethargic. Her eye also looks to have a small infection. She has been eating very well. Is there anything we can do for her instead of taking her to the vet.