I have a trigger on Opportunity that updates a text field on the Opportunity called WhatChanged__c. It's comparing the values on two related Opportunities and seeing if they are different. I need to reference the Field Label in the WhatChanged__c value, and I want to make it dynamic so that if we change any field labels/api names in the future the code will automatically handle the change.

Here is the relevant part of trigger:

//continue if there are cloned Opps moving into the pending stage
    if(!pendingClonedOpps.isEmpty()){
        
        //get all the labels for Opportunity fields and put them in a map, keyed to the field api name
        String objectType ='Opportunity';
        Map<String, Schema.SObjectType> schemaMap = Schema.getGlobalDescribe();
        Schema.SObjectType leadSchema = schemaMap.get(objectType);
        Map<String, Schema.SObjectField> fieldMap = leadSchema.getDescribe().fields.getMap();
        
        Map<String, String> fieldAPIName = new Map<String, String>();
        for(String fieldName : fieldMap.keySet()){
            fieldAPIName.put(fieldName, fieldMap.get(fieldName).getDescribe().getLabel());
        }
                
        for(Opportunity opp : pendingClonedOpps){
        
            //List to store all of the names of fields that have changed
            List<String> Changes = new List<String>();
            
            //get the related Cloned Opportunity record
            Opportunity clonedFromOpp = ClonedOppIDToClonedOpp.get(opp.ClonedFrom__c);    
         
            if(opp.Buyer__c != clonedFromOpp.Buyer__c){
                String fieldName = 'buyer__c';
                String Label = fieldAPIName.get(fieldName);
                String oldBuyer = clonedFromOpp.Buyer__c;
                Changes.add(Label+': '+oldBuyer);
            }    
 
            opp.WhatChanged__c = CSUtils.join(Changes, ' ');
      
        }

It's working, but the part I'm not happy with is the line String fieldName = 'buyer__c'. If the API name for that field ever changes, I will need to update the fieldName variable. Is there a way to dynamically get the API name, in a similar way to how I am getting the field name? Can I create a Map that stores <Field, String>? This is my first time working with Describe.field() methods so I think I'm confusing myself!

Any help is much appreciated! Thanks!