You are suffering from painful period which is called dysmenorrhoea. You can take anti spasmodic medication like mefenamic acid
to get relief from this.
Also you should avoid coffee/ salty/ junk food stuff in 2nd half of cycle, take balanced diet with more vegetables and drink plenty of water, keep bowel habit regular and take adequate rest. You may take hot/cold compression in alternate way.
To delay your period, you have to take norethisterone
pill (like Primolut-N) 5mg thrice daily 3-4 days prior to expected due date till you desire. You get withdrawal bleeding within 7 days of stop taking the pill. Some side effects like nausea, vomiting, abdominal cramp
, irregular bleeding etc may occur.
Be well and take care.