How can I register live-in relationship in India?

Sir, My GF is 19 years old and I am 20 yrs old. We can't marry because I don't have legal age. Her family is torcher her and restricted her to not going outside home and not using mobile after knowing our relationship. We love each other since 1.5 years. We decided that she is going to leave her home and we both live in relation. She will find a job we will manage. Please guide us legally.