Creaking Subaru Legacy Wagon

I have 2005 Subaru Legacy wagon GT and when i go over bumps that make the car rock side to side i get a creaking noise from the rear end ( i think is sounds like its the rear suspension)

Any Ideas as to what it could be and if i should get it fixed.

I would go get a suspension specialist to check out your suspension. Whatever the issue, it needs repair. Could be a strut issue or something else.

…or, it could be merely dry bushings on the anti-sway bar.
In any event, it needs to be put on a lift for evaluation.