Teeth whitening worries ㅜㅜ

My teeth are a bit yellowish. I decided I definitely need to get whitening after my braces treatment! However, I was so tired and sore from the orthodontic treatment that I didn't get around to whitening.

I'm afraid to do it. They say whitening makes your teeth whiter, but I heard it can also cause sensitivity. I'm also worried about the cost. I'm curious about reviews from people who have tried teeth whitening.ㅠㅠ