Could Vomiting After Tummy Tuck Cause Injury?

Hi there-
I'm sorry you were so sick. The risk that you injured yourself or compromised your tummy tuck result really depends on how far removed from the operation you were when the vomiting started.
The earlier in the recovery period, the higher the risk that your muscle repair had not become strong enough to support strong retching and that this caused your repair to fail.
After 6 weeks, however, the repair should be quite strong and the risk low, in which case the discomfort is probably related to stretching of the underlying scar tissue during the vomiting.
It should be fairly obvious whether or not your repair is intact, though... if you have disrupted the sutures, I would expect to see a round shape where you had previously been fairly flat.
In any case, the best person to advise you would be your surgeon, who has the benefit of knowing the details of your surgery, and can, after an examination, determine if you have experienced a change in contour.

At 8 weeks you should be OK.  Vomiting certainly in the early post-op period could cause tears in the diastasis repair. Pain at 8 weeks is probably normal but I would follow up with your doctor.