I would like to block all user registrations,
Go to your dashboard and turn off registration.
keep discovering pages on my blog that I did not put there... pertaining to viagra and prescription drugs..
Safe bet you have been hacked in one form or another.
I don't have a clue which version of WordPress I am using.
Not knowing what version you currently use seems to be a common precursor to getting hacked.
Visit your front page, view the source, see what version you have. From there, you can most likely view some of the "pharma-spam" crap as well. Or.. log into your WordPress site administration panel and it will tell you what version you are using.
At the very least, you will need to search the forums for guidance and assistance on getting "un-hacked". There are an unlimited number of references. Usually the keywords "hacked" and your wordpress version number will suffice in a search, either here or on Google.