List entries for a single tag from blog section
You were very close! You are looping through craft.entries.section('blog') which doesn't use your tag query. You simply need to loop through the results of your query which you've set in the entries variable. 

You may want to grab your weddings tag using the tag's id or slug as .search will find any tag with the string 'weddings' in it. 

It might also be a good idea to use the conditional to check entries is returning something first, before outputting it.

{% set tag = craft.tags.slug('weddings').first() %}
{% set entries = craft.entries.relatedTo(tag) %}

{% if entries|length %}
  {% for entry in entries.limit(5) %}
    {# get stuff #}
  {% endfor %}
{% endif %}