i am building an education site ?did i need to register with any copyright office.did without registering at any office , i have no rights to own my content.

Just by producing copyrightable work you automatically have the copyright. The only advantage to "Registering" your work is to prove that it is yours. If you have published it on the web there is no doubt that it is yours and when you produced it. Answer No you do NOT have to register to be protected but you DO need to publish.

The only reason why you might register is perhaps to show your site viewers that you are genuine and honest, not a scam. The certificate will give you a stamp of authenticity. You might add your degrees as well, if there is any.