First born clingy, baby # 2 is cooking

So about a month ago I found out I was pregnant with our second, shocking news. As weeks have progressed my son who is 16 months now is SO CLINGY to me. He is usually not like this at all. Do you think he feels there is something different? I know he doesn't understand I'm having a baby but I wonder at the same time. Before i knew i was pregnant my dog out of no where got extremely protective over me. It is just so weird. I can't do anything without him having to be touching me or right next to me. And sleeping has completely gone out the window. Anyone else have any experience with this?