wp-admin not working after adding HTTPS

I just added a certificate to my website – pradyotghate.com. The certificate is working fine (https://www.ssllabs.com/ssltest/analyze.html?viaform=on&d=pradyotghate.com).

I have updated the WordPress Address and Site Address to use https://pradyotghate.com and the site seems to be working fine (with mixed-content warning and CSS not loading, but not worried about that).

My bigger worry is that now when I try to load wp-admin page, I get –
The pradyotghate.com page isn’t working
pradyotghate.com redirected you too many times.

I have added following to the wp-config.php –

define('FORCE_SSL_ADMIN', true);
define('WPHTTPS_RESET', true);
define('FORCE_SSL_LOGIN', true);

but that is not helping at all.

Not sure why the website works but the admin panel won’t. Please help.