There are similar issues faced by many couples in love. You have known the person from 7 years and comitted since a year and in a live-in relationship for 6 months.
This is ample time to know the commitment from both sides. If your partner is of the legal age and you both are truly in love with each other, then you cannot be forced into a marriage against your choice. This is the legal aspect.
Now, coming to the soical and familial aspects, parents of a girl will often be hesitant to agree for an inter-caste or love marriage. They would be more worried about whether you would be well looked after, would you have enough money and support to lead your life well. What would the society feel, how would the relatives treat them, what about the other children in the family. These are the questions that run in the mind of the parents.
So, you need to understand, there concerns too. Firstly, no need to get depressed, give the issue some time to settle down. Focus on your studies and keep yourself occupied.
When you find a chance, you and your partner have to have a serious discussion as to who committed you both are, is your bond of love strong enough to oppose parents if neccessary.
Then have a meeting between both families with other well-wishers from both families and both of you. have a discussion and try and re-asssure them so that their anxiety and fear is lessend.
You may need to have a few discussions and be prepared for a harsh excahange of words. Let your partner also speak to your parents.
Then if still things are pending, give your parents a choice of allowing you to get married to the boy whom you know or sit at home without getting married or marrying against there choice. If you go down this route, you both as a coule should have enough support to help you as starting a new family, managing the finances (home,rent, gorceries,travel, other expenses) are not easy. You boht need to have a job or at least the boy should have a job before you decide to consider marriage against the wishes of our parents.
If you have enough support and the love between both of you is true and strong, then you both can go ahead and get married. IF there is any doubt in support and love, then re-think.
Even if your parents dislike the wedding, with time, arrival of a child, their anger comes down and after a few months would be happy to welcome you back.