The same number of characters in two parts of the regular expression

To begin with, I am using PHP and preg_replace

I created some regex /(={2,6})\W+(={2,6})/

to try and match

Lorem Lorem Lorem Lorem Lorem 
==Etymology==

==Links==

Lorem Lorem Lorem Lorem Lorem

      

        
        
        
      

    

( http://pastebin.com/5kAKQM1x )

so I can turn it into

Lorem Lorem Lorem Lorem Lorem 
==Etymology==
<<My Insert Here>>
==Links==

Lorem Lorem Lorem Lorem Lorem

      

        
        
        
      

    

( http://pastebin.com/aamRSXU4 )

The problem is that my regex also matches

Ussher believed the whole creation process occurred on that day.

==Religious views==

===Jewish traditions===
In rabbinic writings and the

      

        
        
        
      

    

( http://pastebin.com/HJ2Vy7Md )

How can I ensure that both sides have the same number of characters =

? How to use {2,6}

in different ways.