You don't mention either Watts or Volts so nobody can answer you accurately.
If your shower has always been popping the breaker then the breaker MAY be under rated but the shower is more likely to be faulty in some way particularly if the breaker tripping is a recent happening. A certificated specialist is probably your safest route.
Your question, by the way, is in the category Electric Shavers.
Peccavi
August 2009
Automatic Answer
While you wait for answers, we may have found some information which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix baths and showers.