What makes you believe that this is a negative entity attachment?
I feel that it may just be some negative energy that is being released. When you meditate frequently at first, sometimes a lot of negative energy is released, and this can take a toll on the body/mind/emotions. The first time I did a chakra clearing for my wife, she had a rash break out all over her body for several days with no other logical explanation of its cause.
I just cleared out some energy yesterday that has been bothering us for a while, and it made a huge difference in both of us. Negative energy doesn't always mean a negative entity.