Using www.domain.com instead of domain.com

Ok, so I just upgraded two of my blogs to the latest version. However, something is not right.

Both the domains, are automatically redirected to https://stackians.com and https://theopendirectory.biz/blog instead of the ‘www’ thing before the domain. The problem is, that the https://www.domain.com has a PR and that is what I would like to keep.

I tried solving this by a 301 redirect in my .htaccess (i know, it was foolish to do so).
However, firefox gave me a message
‘the website is redirecting in a way that will never finish’.

So, i believe, the .htaccess forced a redirect to https://www.domain.com while something in wordpress forced the https://www.domain.com to redirect to domain.com

Really need help on this!
Please..!!