Is it normal for a boy to give me a cold shoulder, ignore me and stop looking for me after his confession is rejected by me?

Not normal. On the one hand, your refusal is just an attempt to express his confession, which does not mean that he will ignore you; On the other hand, even if you are lovelorn, he should not forget your existence or treat you coldly. Moreover, if he really likes you, he may insist on expressing his feelings, or at least give you some warm-hearted treatment.