E.S.
Hi there,
As it's 3am while I'm writing this while my family is sleeping peacefully (but I'm not) I can certainly relate. In fact, my baby is 11 weeks, too!
I liked your reasoning that perhaps you were "alert asleep" and thats why you were waking. However, I can reassure you- my baby is not sleeping more and more, so perhaps that is not the issue. I also worked out yesterday, and got my 30 min of activity (plus playing with my 3.5yo). I'm going to look into the prolactin insomnia that SB described.
I do find that the teas from Celestial Seasons Sleepytime Vanilla or Tension Tamer help me to reenter the drowsy state. It's not 100%, but it helps. I also try and look at it as "me" time, which makes my wakefulness almost ok.
Best regards & sleepy thoughts!