Mom not supporting Marriage - earlier was in support..what to do ?

Hi ,
Im 21 yrs old and I am in love for the past 3 yrs actually my mom at the beginning supported my love and now she has turned towards me saying that he is not the one for me but I really love him to the core adontont want a life without him now they planning for my marriage at home. His parents know about this and since his sister did not get married they are not ready to come and speak at home.. I am in such a worse situation that I really go out of my mind.. I would really be thankful if u suggest some ideas for me

Very short description, I think you should provide more details. You have also not shared why Mom started saying that he is no more suitable for you, what made her to think so ? Any incident or action against her will ?