Randomly deleted posts? and spam!

I’ve made at least two posts this week, and a couple the week before, but suddenly when I checked my site, all of the posts for this month were gone! They were there last night but when I got up this morning, they were gone!

I’ve also had a problem with people spamming my comments, and leaving random and/or inappropriate comments. Could the two things be connected?

How do I keep this form happening again? (I’ve already disabled comments).

Second, how did these posts get deleted?