how do i know if google has blocked my site?

Generally, if Google have issued some kind of negative action against your site, you will be notified via the Google search console. There is a section here that will focus on penalties and other negative actions they have taken. They will give a reason for it and possibly a way to undo the action assuming it isn't a severe breach of their terms of service. If there is no notification, it can be hard to tell. It may just be badly optimised pages on your site. Check the metrics in the search console to make sure that your pages are being indexed. If they are still indexed, you are not being blocked. Your site may just have too many technical errors for them to consider it worth showing at the top of the search results.