Have a good think back over the last few weeks, who have you given your email address to? Have you bought anything over the internet? Have you, (or the teenagers), enrolled for any web sites?
A possibly answer is that your address has been sold on to the spammers, maybe an organisation you decided not to do business with, like buying software etc.
I use Mailwasher Pro with a reporting and bouncing facility, that reduces spam to a bare minimum.