It is undesirable to marry without the consent of parents. However, if you have made the eijab and qubool (offer of Nikah from one side and acceptance from other) in the presence of two legal witnesses then as per the Shariah the Nikah is valid. But the family members should be informed so that they may not think ill of you. It is makrooh (undesirable) to use contraceptive measures.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband