noise in rear of car, maybe brakes??

[99infiniti30t]

i have a 1999 infinti i30t and its been baby'd at the dealer since i bought it about 7 years ago, due to financial struggle i turned to doing the work on my own. i know enough mechanics to change brakes, oil, etc. changed the rear brakes about 3 days ago, and put brand new ceramic ones in place of the old ones. the next day i noticed a noise in the rear of the car, almost like a thudding noise, like the jack or something was rolling around in the trunk. (which isn't because its all secure in the back). The noise happens in random times while driving, i'm almost positive it isn't the brakes, but if it is, what did i mess up on? any suggestions? i properly installed the brakes, bought the $10 tool from autozone and turned the rear piston clockwise like stated. so.....anybody else have this problem?

[loystock]

Did you torque the lug nuts to @ 80 ft-lbs? Loose lug nuts can cause the wheel bearing to fail or worse, the wheel to come off. On the other hand, over-torquing can damage the wheel/rotor. Did you disconnect the parking brake cable when you replaced the pads? If so, did you reconnect it? Verify which side the noise is coming from. Check the lugs nuts tightness and if needed, remove the wheel and inspect the brake installation.

[NutriaforBreakfast]

On the rear brake pads there is a raised dot which has to go in the groove of the rear piston
caliper gear. If you dont put the dot in the groove, you wont have a good rear brake installation.
The brake pad will feel likes its too big unless you do this. You will want to use a torque wrench
and tighten all the brake components properly too. Dont overtighten per Loystock above as this
could bend your rotors.

I got some pads from Auto Zone that didnt fit well one time and had to take them back. Ended up
using dealership pads with no problems.