I have two objects opportunity and price study.Both are related using lookup relationship.
In Opportunity I have picklist called Rule__c with value "rule" and others.when I select a value "rule" I need to insert price study record.for that i wrote a trigger:

trigger InsertEPRecord on Opportunity (after insert,after update){
 List<Price_Study__c> Pricestudy = new List<Price_Study__c>(); //Initialize Price Study Object
 RecordType rt = [SELECT Id, Name FROM RecordType WHERE Name = 'Price Study']; // Quering Record type Name 

 //Insert trigger to check condition Rule field value is "rule"

  for(opportunity opp : Trigger.new){
            //Adding Price study record to price study list
           if((Trigger.oldMap == null || 'Rule' != Trigger.oldMap.get(opp.Id).Rule__c) &&  opp.Rule__c=='rule'){
            Pricestudy.add(new Price_Study__c(Opportunity__c = opp.id));
        }    
    }  

 //Checking Null and Insering Price study list   
    if(Pricestudy.size()>0){
    insert pricestudy;
    }
}

When price study record is inserted it should update parent field value called EP_insert__C.

trigger UpdateAmount on Price_Study__c (after insert){ //Trigger to Update Opportunity EP Field value
  list<Price_Study__c> pslist=new list<Price_Study__c>();  //Intilaize Pricestudy list
  set<Id> listIds = new set<Id>(); //Set of opportunity Ids
  set<Id> pricestudyIds = new set<Id>(); //Set of price study Ids

   //Perfroming Tirgger Insert Operation
  for (Price_Study__c childObj : Trigger.new){
    //Storing of Opportunity ids in variable listids
    listIds.add(childObj.Opportunity__c);
    //stroing of price study ids in variable pricestudyIds
    pricestudyIds.add(childObj.id);
  }

  list<opportunity> opplist = new list<opportunity>();
  //set of pricelist to update opportunity field value 
  for(opportunity opp: [SELECT id, EP_Insert__c,(SELECT ID,Opportunity__c,Auto_Number__c,Current_Year__c FROM Price_Study__r) FROM Opportunity WHERE ID IN :listIds]){
    for(Price_Study__c p:opp.Price_Study__r){
     opp.EP_Insert__c = 'EP/'+P.Current_Year__c+'/'+P.Auto_Number__c;
     }
     opplist.add(opp);
   }
  //DML Operation
  update opplist;
}

Every time I am testing my first code it is working fine .it is insert one record on price study object.
When I am testing together with both triggers they are inserting two price study records.Seriously I cant able to find where the issue lies.
Please help me regarding this.let me know i am unclear.