Your scenario is very common in India. You have not mentioned your(and the boy's) age or education.
Inter-religious and Inter-caste marriages (especially if the girl is from a higher caste) has many issues. It is common for the couple in love to find that they are targeted for emotional, social and verbal abuse. There are instances where in physical violence and even killings happen in geographic locations wherein the caste-based hierarchy is rampant.
You are living a newer generation and thinking with an open mind. Parents of girls are often worried about the social isolation and being shunned off by relatives if there is an inter-caste marriage. Parents also worry about the other siblings that have to be married ( after you in your case).
Genuinely, they love their daughters, it is fear of the society (that makes them/treat them as outcasts), sense of humiliation (yes, for some fathers it's loss of face and reputation, if the daughter marries a lower caste boy), the issues with financial security and being able to lead a decent comfortable life.
The other side of the story is sometimes people start loving with an intention of financial gain and property. You should be careful about this.
If you and the boy are of the legal age, then review what you know about him, is it infatuation or true love. Keeping emotions apart have a frank discussion as a couple in terms of the bond of love between you both. Can it withstand the social and financial stress?
Assume that you both have to get married moving away from the family. Are you prepared for this? Do you have a job or does he have a job? do you have a handful of well-wishers or friend that you can fall back for support and help? It takes a decent sum of money to run a family (rent, travel expenses, food, clothing, medical expenses, food, the arrival of the first child etc).A lot of couples in love face a strain or anxiety when the reality of married life sets in.
Once you review all these, then have repeated discussions with your family, highlight the fact that you would be happy,you would wait for their change instance, if needed you both would move away from home to a different place for a few months until things settle down. Initially, you would face strong resistance, you need to have patience, persistence and the maturity to understand the fears of parents. You have to slowly ally their fears one by one.
In a couple of months, you would get an idea of the family's decision, then you can give them a time limit and mention that you are getting married with or without their wishes. Then you both have to be mature enough to start on your own and after some time once the anger of the parents settles down, you can try and reunite with your family.