Maybe he is too big for his bassinet and hitting the sides in his sleep, waking himself up?
Maybe a wonder week?
Maybe he's just being a typical unpredictable bub hehe, my DD was a great sleeper and the last week is now waking through the night.
I've heard that learning new things can unsettle their sleep. My dd is just becoming mobile and her sleep is out of whack.
I doubt it very much that you're doing anything wrong. It's probably just a phase and hopefully he will be sleeping through again soon.