Here are some ways of finding out if your friend has blocked you on Facebook:
Ask mutual friends if the person whom you suspect has blocked you is still on their friends list. If they can view his or her profile, it is a good sign that you have been blocked. Go through old conversations with that person. Click the 'Actions' button and select Report Conversation. If you see 'Blocked' next to the person's name, this means that you have been blocked by the person. If you see 'Report' instead of 'Blocked' then it implies that the person has deactivated the account. Access the person's profile link. If you get a "Page you requested was not found." it is either you were blocked or the account has been deactivated. Try to access the profile link with a new account or another account to know for sure.
Only the person blocking you knows they have added you to the block list. One way you can attempt to find out is by searching their name in Facebook if you have been friends on there before. If you can't find them anymore, it is possible they have blocked you.
try and go onto their page by typing in their name in the search bar, if their page which you used to be friends with doesn't come up, then that means that they have blocked you. I hope my answer helps you... kinda! xxx