I succeeded in fighting a saggy male chest via standard push ups. When I was working out my lower pecs by incline push ups and finished the routine, I saw the left side of my chest is bigger than the right side, and I wondered why? I always check my posture and balance before going to do push ups, although I am a left handed person.
Whether it's normal or not depends on how significant the difference is. It's normal to be slightly asymmetric. No part of your body is exactly symmetric.
If it's significant enough for it to bother you, then you should consider doing exercises that are independent for each pec muscle. This is useful because, even though you try to balance it, with a push up or barbell bench, your body can compensate for a weaker side by pushing the weak side up faster. The physics of it makes the weight shift to the lower side. With something like one arm pushups or dumbbell bench, it's impossible to shift weight from one side to the other, so you should have equal development.
To clarify in response to your comment below, you should do this independent exercise equally (same weight, reps and sets) for both sides. This will be easier for the strong side and harder for the weak one, so the weak one will grow more. Not doing so could possibly create imbalances where before you had none. For example, only doing one arm with dumbbell bench could cause an imbalance in your biceps, since the biceps is involved as a stabilizer in db bench.
It is my understanding that everyone has a dominant pectoral muscle - one which can have greater anchorage on the anterior surface of the sternum. Often it is the perception that you are able to affect more precise control on one side of your body than the other - it is the mind-body connection at play.
to fix uneven muscle is simple look in the mirror and find out which part of your muscle is bigger or smaller than the other mark that point and hit it with high reps with 4 or 5 set with extreme squeez...improve your weakness part by visualising wat exercise I should do to make this right whatever it takes feel the muscle and pump it..