What's the best way to resolve constipation 4 days after a Tummy Tuck?

You seem to be doing all the correct steps to try and get things moving along. Constipation post surgery is a very common occurrence. It is mainly caused by taking narcotic pain medication, so if you have not already, try switching to something non narcotic such as ibuprofen and make sure you are also drinking plenty of water. 

Sorry to hear.  Constipation is quite common after tummy tuck--most often because of the narcotics.  You have done all the easy things.  There are lots of choices for next steps (Dulcolax suppository, Fleets enema, and magnesium citrate as a last resort), but you should check with your surgeon first.  Every surgeon has their preferred methods of dealing with this.  Good luck.