What you are feeling is real. Not feeling like yourself is common. Mood swings are common, no one minds if your really happy but if really angry thats different. Having that feeling of somehow being different than before is common also. I have never been able to describe it all that well. Any attempt I made is too vague for my liking. I just know I am different. Not worse personality wise just different. Maybe it is the sum of all the individual differences.