Is there any way to block him please and to prevent him from seeing my posts?
There is not. Ultimately this is a public forum and you can view posts without even having an account. So if you could block someone from viewing your posts.. they could just log out and view them. The best advice would to be use an account with a username which doesn't have personal details such as name, date of birth, major interests ect. This in the first place will limit the number of people able to find you. As well as not posting in too much detail, where necessary switching to the anon function (In life and style sections).
If you have an issue with a user who is perhaps making you feel uncomfortable with acts such quoting every post; then you can make a thread in THIS SECTION and let the community staff know. They will investigate and action as necessary.