My site to denial of service attack..What do I do? Help me

My website has been under denial of service attack or dos attack , so my blog and WordPress does not work .. i block the many ip and found the same problem .. when i put the cloudflare system Iam under attack the problem will be solved ..

my Site without cloudflare Iam under attack mode does not work ..
i have contact with the hosting they give many of ip and said you must deny them. i do it but the problem still.
i add many of plugins such akismet,captcha, wordfence and spam free and w3-total-cache but the problem still show me and my website been slow. the problem is only with wordpress blog but another html page dont show me this problem.

I want to Prevent dos or ddos attack permanently without iam under attack mode … how??
Is there a professional way … What do I do?

my site: sumeronline.com
help me. thanks