My blog site hacked

Am running a blog-site, and using sonar-theme on my blog.
hacker hacked my website 4 times.I report to my hosting provider but they told me problem in th your theme.

Hoster says: “The theme you are using are being exploted for hack, please login at https://www.funnybunnyvideos.in/wp-login.php and change your theme to fix this. Please use theme from reliable source only.”

Now am tried to prevent hack my blog. What should i do now.