What? When? Why? How?

What is this feeling I'm feeling? I've only known you for about a month yet why do I feel this way towards you? I thought that such feelings have already been cast aside when I decide to lock myself in my own world. When did I let myself fall for you? How did you manage to slip past my defenses and slipped into my heart? Why do I feel sad of the imminent separation when I'd known that it would happen at the very start?