The fact that you have a CC of 3 means that your chlorine is killing off something in the pool, and that your beginning chlorine level after the shock had to have been higher than the 25 that you were expecting. Total chlorine = Free chlorine + Combined chlorine, so you must have started at TC of 27. What you're going to need to do is maintain that shock level until you see the pool clear up, and your CC goes down to 0, in addition to not losing any chlorine overnight.

How are you testing your water?