Did I damage tummy tuck muscle repair by doing too much too soon? I've had shooting pain in my abdomen after lifting.

Early out of tummy tuck surgery, the concern with your description would be, the potential for disruption of sutures that are holding the abdominal wall muscles together in the midline. If enough disruption occurs, the result could be separation of the abdominal wall muscles and localized or complete, abdominal wall laxity ( similar to preoperative situation).

In general, it would take a significant amount of pressure to “tear" the muscle repair after tummy tuck surgery. This event would likely be associated with significant discomfort. A change in your physical examination, such as increased swelling, bleeding, a new onset "bulge" would also be likely.

Generally speaking, abdominal wall muscle plication performed during tummy tuck surgery is quite secure; disruption is very unusual. You will be best off following up with your plastic surgeon who will be your best resource when it comes to accurate assessment, advice, and/or meaningful reassurance.

Best wishes.

More than likely you did strain your muscle.  This will respond to rest. Your surgeon should have given you lifting restrictions. Please follow them. 

I doubt that lifting a pre-K student significantly disrupted your tummy tuck muscle repair.  By 4 weeks she should be well on your way to healing.However it is very important that you see your plastic surgeon for an examination.  Your surgeon will be able to examine the repair to make certain that no damage was done.