create programmatically a new item of a collection field

Hi,
I need to to put values from a node in a collection field placed in a form.
My problem appears when I need to create 'new item' of the field collection.
For example, in my node I have two items of a collection, I need to put two item in the form with the value of the node. When the user open the form, there is only one item.

My code is working, I can see two items, the values are OK, but when I save the form, the new item of the collection created are not saved in the node.

$loaded_node = node_load($record->nid );
//if the node exists and the data of the form are empty, then create the list of the collection value

	if ((isset($loaded_node) && (empty($form['field_onglet4_fiche_analyse']['und'][0]['field_fiche_intitule']['und'][0]['value']['#default_value'])))) {
		
		$wrapper = entity_metadata_wrapper('node', $loaded_node);		
				
		$item_count = -1;
			
		foreach ($wrapper->field_experiences as $i) {
			$item_count++;
			// add new item if needed
			if ($item_count>0) {
				
				// create the field_collection item
				// $field_collection_item = entity_create('field_collection_item', array('field_name' => 'field_onglet4_fiche_analyse'));
				//associate it with the node array
				// $field_collection_item->setHostEntity('node', $form['#node']);//logically I read to put setHostEntity('node', $node) but I'm working in a form
				
				$field_collection_clone = $form['field_onglet4_fiche_analyse']['und'][0];
				$form['field_onglet4_fiche_analyse']['und'][$item_count] = $field_collection_clone;	
						
			}
			
						
			//prepopulate the fields
			$form['field_onglet4_fiche_analyse']['und'][$item_count]['field_fiche_intitule']['und'][0]['value']['#default_value'] =$i->field_exp_emploi->value();
			$form['field_onglet4_fiche_analyse']['und'][$item_count]['field_fiche_structure']['und'][0]['value']['#default_value'] =$i->field_exp_lieu->value();
			
			foreach ($i->field_exp_taches as $j) {
					$infos_onglet2.=$j->value();
					$infos_onglet2.=' , ';
					
					$form['field_onglet4_fiche_analyse']['und'][$item_count]['field_fiche_missions']['und'][0]['#default_value'] .=$j->value().' <br> ';
					}

		}

Thank you for your help !