I feel I'm a jerk right now. Cause I have a girlfriend, I loved her, but recently, I just feel I don't like her anymore. I don't know why all things be this. Maybe, I like another one. However, I can't just break this relationship like this, I can't hurt her heart. So, what can I do? Help me, please. By the way, we've loved each other 4years.

Maybe she feels the same way about the relationship?

Regardless - you aren't doing her or you any favors by hanging on. It is okay to fall out of love and you are not responsible for the way she reacts to it. Hanging on in the end is more hurtful. The relationship will just deteriorate but you will not have your heart in it.

So man-up and do the responsible thing.

Try some honest communications and resolve this impasse one way or another. Not being honest is like lying. Having no courage to do the right thing only makes you both more miserable. Nobody wants a partner who doesn't like them. Would you?

4 year long time. Both of you invested long time in this relationship. I don't know what causes you feel dislike her but whatever it is, evaluate it. If you are completely sure about it then talk to her with details. It will be unfair to her if you will stretch this relationship. You said you may like someone else. So just be honest with yourself and her. End it properly.