this is not me anymore

Have you ever felt like... that is your body, but inside is not you? everything has changed, since that day.. i decided to turned into a good, nice, and wise girl. but in fact i cant do that. in same time i feel so weird, my heart said "hey, its not me"
some people said "this life only once, we are also still a teenager for what we are serious in a relationship? we must focus on the lesson. It is important at this time"

Now.. i felt so weird, very weird. what can i do? i'm happy with him, but now he's changed. i love him, but now . i'm confused. I felt uncomfortable with him again. I can't be myself anymore. I feel like a doll that should continue to hold and cover up my emotions. and thats slowly hurts me. but i loved him very much, what should i do?