Once i faced the problem i googled and found some topics about the problem.
Result of the discussion I found solutions which might help you in same cases.
If you still haven't figured out how to skip the loop - add "index.php" in address bar after "youdomain.com/wp-admin/" ( In result you will get "http://www.yourdomain.com/wp-admin/index.php" ) . It will allow you to access normally wordpress admin page without loop.
Method 1Check general settings ( settings -> general ). And make sure your addresses are same ( make them lowercase ).
Method 2Go to Permalinks settings ( settings -> permalinks ) and change to plain.
Method 3 ( My situation )None of first methods worked for me ( Method 1 was correct for me, and method 2 - i didn't wanted to change permalinks ). So i have checked code what is happening there... and noticed that index.php isn't loading on wp-admin/ ( which should.. ). So I have checked ".htaccess" file in dir ( and in root dir later ). And I found old code in .htaccess which ruined login process.
I have removed everything but wordpress comment surounded code, saved and wuallia... everything worked.
Let me know if it worked for you. Thanks for comment <3 p="">