Gabie has a wealth of experience working in education.
Great question. I too love English and would love nothing more to do it all day.
A PhD in a relevant field will allow you to apply for jobs that research and lecture at universities. Please note these are very competitive.
With a PhD in literature you will be able to teach in a High School, write articles and books, and work in non for profits. Depending on what type of specialization you took would change your job prospects.
I hope this helps.