Impacting can be dangerous for a dragon. If it hasn't pooped for a week - my advice is to take it to the vet.
They can actually die from it. If the isn't serious - yet - try to bathe the dragon in lukewarm water
(about shoulder deep) for half an hour and see if that helps. Water usually makes the dragon relax so it can poop.
Don't leave the dragon alone when it is in the water. See "Bath"
Also see to that your dragon gets enough fluid. If it is dehydrated it will be more difficult for it to poop.
Offer your dragon water every 2-3 day and mist it every day. See "Water"
Cicero and Teo in the bath