I’m sure for some this is a point of pure pedantry, but it bugs me nonetheless. Let me clarify:

• A blog is a particular type of website that contains many blog posts.
• The verb use ‘I am up updating my blog’ is appropriate, but not ‘I am writing a blog’. (Technically, I appreciate you are writing a blog, but it is more likely you mean to say ‘I am writing a blog post’ or ‘I am blogging’.)
• A single entry on a blog, like this one, is a blog post (or simply a post, if you prefer).

You are very welcome.