I had my teeth whitened, and they are already yellow again. Why is this happening, and how can I stop it? (Photo)

I recently got teeth whitening laser i-e 2 days back but now i feel that yellow color of my teeth is coming back and i m very upset with this. Could u pls guide me why this is happening and what can be done to stop it. Pictures of my teeth are provided before and after getting the treatment and the current color Thanks