Steering looseness

Everything was fine with the car, but I had to do a few repairs on the car. I changed both front cv joints, brakes and rotories. I changed the passenger wheel axle because the barren was worn out, and changed the control arm and the head of the tire rod because I had damaged the threads. I also put in an a/c compressor. Well I'm writing you to say that eveything works perfect except for now there is a looseness in the steering wheel. After turning left or right and straighten out the car I see that the steering wheel is at an angle instead of centered. Every blue moon the car will not straighten when I turn the steering wheel after changing lanes, and I have to quickly***** it. Im at a lost because this has never happen to me before, all of a sudden having a looseness in the steering. I check the tires and steering, and they both are balanced and aligned. What could be the problem?