(non) Multitasking

I thought I was a good multitasker. I really did. I've discovered recently though that certain things are just not meant to be multitasked (is that a word?). Say for instance listening to an audio book and reading/typing on the internet. I can't do both at once. Half of a chapter will be gone and I'll have no clue what I just listened too. Has it always been that way or is it just my fried brain? I can't remember. I'm blaming it on the kids. Pregnancy turned my brain to mush.