Allowed Memory exhausted and 500 Internal server error keeps coming back

Ok, I’ve been struggling from this for the past few weeks and it keeps coming back.

First off, I have an “Allowed memory size of 67108864” and then I tried this from another thread:

1. Try adding this line to your wp-config.php file:
define(‘WP_MEMORY_LIMIT’, ’64M’);

2. If you have access to your PHP.ini file, change the line in PHP.ini
If your line shows 32M try 64M:
memory_limit = 64M ; Maximum amount of memory a script may consume (64MB)

3. If you don’t have access to PHP.ini try adding this to an .htaccess file:
php_value memory_limit 64M

and now 500 internal error is the error.
This happens before and I tried this one: http://www.wpbeginner.com/wp-tutorials/how-to-fix-the-internal-server-error-in-wordpress/

and it worked for a few days and now it happens again, back to the Allowed Memory Exhausted.

wp-config, php.ini and .htaccess is now with a 64mb limit, this should now work but this error keeps coming back.

Anyone has an idea?