22 month old not sleeping

Stacigirl413

Hi ladies

I am not a usual poster in these boards and I lurk from time to time.  Question about my 22 month old son and sleeping.  Let me preface the question with my son has been an amazing sleeper always and has slept through the night since 6 weeks.  DS night time routine has always been the same and there have been no big deviations from it, dinner, bath, bottle, we read a story, play a few little games (nothing too stimulating), watch at TV show etc... and he his usually in bed no later then 8:30p.  As of recently (maybe the past 3-4 weeks) DS has been waking up not totally in the middle of the night, sometimes 11 sometimes 1 its all different and cries "momma, momma" I go in or DH goes in and as soon as we are in his room he lays back down and sleeps.  He wants us to rub his back for a few minutes or rock him (which is VERY new we never did this in the past) but generally goes back to sleep after a few minutes.  

I'm just curious what has him waking up??? Is it possible teething, but he doesn't seem like he's in immense pain, is it growing pains, and the other thing I can think of is I am currently 7 months pregnant is it possible he is aware of the baby coming in some way?

Any advice or direction would be greatly appreciated.  Thanks ladies in advance for all your help and support