severe front tooth pain

One of my front tooth is extemely sensitive. I stopped having hot or cold drinks for nearly a week now as i could not tolerate the pain. It has become worse now, i can feel the pain even if i touch my tongue. If that tooth happens to be touched by the top tooth, the pain is literally killing me.
I have used colgate whitening tooth paste for nearly 2 weeks and after a gap of a week i started getting this pain. I stopped it and i am using sensodyne for the last 3 days. But it is not helping me much. I went to the dentist twice already, did the x-rays and said that the x-ray looks very normal. Dentist cleaned around that teeth yesterday, but still the pain is same. I am completely confused by what is happening to me.
I never had any tooth problem in my life till now. I always clean my teeth atleast once a year.
Can some one please help me. My gums are not that painful, it is my teeth  that i cannot touch with even my finger. None of the pain killers are working. The pain is unbearable. Pls help.

[Jerome Tsang, DDS]

Not sure.  You may want to go to a root canal specialist to see whats going on.  To me, I'm not sure why the tooth is acting up but it sounds like there's a pulpal inflammation going on thats causing your pain.  That'd be my guess.  A root canal may be needed.