When I rotate my viewport view, it always rotates around one of the object's pivot in the 3d viewport and I'm unable to move my camera around 3d view properly. If I move that certain object, my viewport view moves accordingly to that object. I've tried pressing (.) and (5) and other numpad numbers, It doesn't work.
Oh, I just solved it myself. It seems my camera was locked to that object in the N menu in the "view" section. I just removed object from there.