All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The legal marriage contract makes it lawful for the husband to enjoy his wife. The wedding party is not a pre-condition to a legal marriage. In fact, making the marriage contract known to the public is only a desirable act. Nevertheless, if the custom of the people of your area is to refrain from having sexual intercourse with their brides as long as the wedding party has not been held, then we advise you to act accordingly although it is not obligatory upon you, but just to please everyone. However, it is permissible for the wife or her guardian to prevent the husband from enjoying his wife as long as he has not paid the part of the Mahr (bridal gift) that should be - according to the contract - paid in advance. Moreover, it is your right to softly and kindly demand your parents to hasten your marriage ceremony before any appearance of your bride's pregnancy as that may cause problems with your in-laws. Tell your father that the purpose of a marriage is to remain chaste and keep away from temptations, and this could be achieved only by living with one's wife. Seek Allah's help and blessings and ask Him to make your matters easy. You may ask your brother's help to convince your father in this regard.
Allah knows best.