If i was born left handed and was left handed dominated ans then became right handed dominated would it mess up my body when using cell phones ?

No.: No. While there is still some controversy about whether the em radiation and/or electronic signals generated by cell phones may have adverse affects on the human body, no conclusive data exists yet. It is still generally accepted that cell phone use (in moderation) is safe. Still, try to use hands-free devices to minimize em radiation exposure, and don't keep your cell phone in your pocket.

Question confusing: Handedness is generally considered a prewired process in most, with right hand dominant most common. There are many left hand dominent folks, and some where no true dominance exists. (called ambidexterous). If your question is whether a cell phone triggered the change, i'd have to speculate no! someone prewired to do well with both may gravitate to right to fit in or it fits with your activities.