cloudflare adding sub domain

I have a website where dns is managed by cloudflare. I want to create a subdomain for it. currently my blogs are showing at xyz.com and I would like to move them to subdomain blog.xyz.com . seems simple enough, with basic A adjustment to point to different IP address. But there is an issue that I am not able to resilve and I am short on time. This needs to be done on urgent basis. My blogging website is on wordpress and is hosted on aws on bitnami. Problem is that every time I create a subdomain blog.xyz.com I am re-routed to www.blog.xyz.com. For some reason there is some rule that adds the prefix www when request is sent to wordpress site hosted with bitnami on aws. this causes multiple redirects till page eventually crashes. I need someone with experience in server handling who understands this problem. Also since this may require tinkering with .htaccess files I need to be sure that website will not compromised accidently