For a proper advice, documents will have to be seen.
If registration is mandatory as per the laws prevalent then, then you have no recourse but to file a civil suit for injunction against others from disturbing you as you have had possession for more than 20 years. By all means you should keep possession of the property. If society was formed after your ownership in that case also you can see the building plan or floor plan which must and should mention the number of shops. If not, you can complain to the Cooperative Housing Ministry. An Administrator may be appointed.