I just started oil pulling myself. I have done a lot of research on it. I have written a post/article on it which you can read here http://bit.ly/13DIxLQ
Reasons you may be getting sensitive teeth:
1.You haven't Takking a break!! You have to take a break from oil pulling every 4 weeks for at least a week. I recommend 2 weeks! Otherwise instead of pulling all the toxins and bad stuff out it starts pulling your good stuff out! Things like your good bacteria, vitamins, and minerals! This could be whats causing your teeth sensitivity problems.
2.Brushing your teeth with toothpaste! While oil pulling DON'T use toothpaste. Brush your teeth with water before oil pulling. After oil pulling rinse a few times with warm salt water & brush with baking soda or soap!
3.If you had sensitive teeth prior to starting oil pulling it may get worse temporarily which means your body is responding to the oil pulling!
If it continues even when doing all the above things try switching the oil you use. The only oils you can use for oil pulling are coconut, sesame, & sunflower oil. I use Tropical traditions gold label virgin coconut oil which I love! I use it for everything!