Even if your email’s not public, many users get targeted by so-called “dictionary” attacks against their email providers. One solution is to use temporary email addresses, but if you’re already receiving a lot of spam then the problem’s going to remain. So if you’re can’t see your inbox for junk and need a break from hitting “delete” then maybe you should try one of these free services.
http://www.makeuseof.com/tag/top-4-freeware-spam-blockers-work/