بسم الله الرحمن الرحيم
(Fatwa: 226/226/M=03/1435)
You should do taubah and istighfar from the sins of loving and sleeping together before nikah, as it was unlawful. If you intend to do nikah then it shall be better to take any initiative with the consent of your parents. It is also advisable to do istikharah. The family of the girl belongs to Barailavi sect then you should contemplate on the pros and cons of the proposal.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband
