Marriage is a consecrated unification of man and woman. It is not meant for non serious relationships which are destined to break within days or months. Every possible cause should be taken care of before the marriage.
However, if your other half has been abusing you or has been cheating on you, separation needs to be considered. The situation is not safe and sound for you to continue to stay in this association. It is also not a good idea for any children to be kept in these circumstances because of the hostility.