Wmt showing loss of pages in index

As you can see by my attached chart, both my “not selected” and “indexed” pages have both been dropping over the past couple months. I have new content every day. What can I learn from this? What can I do? Have I been penalized?

You are running your blog and forum under same domain name or you have separated it? (For eg. blog.website.com or website.com/blog/)

If you mean www and non-www. I set that feature in WMT a few years ago. Google should only use WWW