What can I do if my girlfriend has refused to marry me after years of

I am in love with a women since 3 years. we had sex many times. we booked a hotel many times. She doesn't interested in sex .but because of my interest she agreed for sex. She promised me that she will marry me. We had a lot of photos together and WhatsApp conversation proof. now she blocked me in WhatsApp and said breakup. She said that the reason is her parents will not agree for the marriage with me. and another reason is because of sex she leaves me. now I'm suffering a lot. I am not focusing at any work .her memories is killing me .I did some mistakes while we are in love. At the time of breakup I begged a lot, please I never repeat that mistakes again. Please give me one chance. I'll change . We will be happy .but she doesn't agreed for that . Please advice me.