Conversation with God and parents

Dear Diary,
Im 21 and my boyfriend and i have become sexually active and we aren't planning on starting a family. I went to the doctor and she suggested that i use Depo Provera but i am uncertain. I am Catholic and am unsure of what God and my parents might think about me using protection as it is against catholic beliefs. I am also uncertain about what my parents and God might think about my being sexually active at my age and before marriage but i do love him and hope to be his wife someday and start a family with him but at the moment i am too young and am not ready for this kind of commitment. I am old enough to make my own decisions and am capable to hadle the consequences but as long as i am happy my family will support me but im not sure what God will think as i have sinned. I hope God will forgive me since i haven't sinned until now.