Teeth Whitening

Hi, I have a coffee stained teeth. The stains are dark brown in color and are concentrated on my front teeth. It is very awkward when I smile. I have tried several techniques to remove the stain, but none of them work. My best friend asked me to seek professional help and to do a tooth whitening treatment from Appleton Dental in Whitby. But, I fear that it will make my teeth more sensitive. Will it have any side effects?What diet pattern should I follow in order to have a whiter smile? Thanks in advance.