I faced this problem with my female red tegu back in May and it took awhile to really get her back on track. She got to the point where she was regurgitating before I realized what was going on, and over a 3-4 week period lost 25% of her body weight. After vet treatment (see below) and a few months of special attention, she's back on track.
Some ideas:
I'd suggest soaking for 20-30 minutes in warm (not hot!) water. Sometimes that helps them defecate.
If that doesn't seem to get the plumbing going, you may need to visit a reputable herp vet. I took mine in, and the vet palpated (felt) some blockage in the digestive track. She provided me with a medicine (also used on humans) that would serve to "gum up" the blocking material and help it pass. This worked for me. I switched to feeding multiple pinkies for a time as well so that the hair did not contribute to further blockage.
Be sure to look at your husbandry. It would be a good idea to feed your tegu outside of its enclosure to avoid the ingestion of substrate.
If you'd like, I can look into what the medicine was that I used.
Dan