Big Problem … Haked i think

Hy,

i have in the past wp-super cache… after the site was bigger in trafic…due to big CPU the host company told me to instal W3 Cache it has databese and other…

After instaling that… after 10-15 mintes i canot login intro my wp acount.. https://www.filmerx.com/wp-admin …. in the past that i was login into my wp… if i login with that it apears me

https://www.filmerx.com/wp-login.php?redirect_to=http%3A%2F%2Fwww.filmerx.com%2Fwp-admin%2F&reauth=1 , and take me to the login screen

I can only log into my wp like https://www.filmerx.com/wp-login.php

Today someone change my permanent link structure… form Custom Structure : /%postname%.html

to default….

Cand you told me how can i discover if iwe been haked… there are some plugin, extension to scan my wp for infections….

My wp site is 3.0.1

Thanks