I assume you mean compete in BB competitions. Competing at 5'10" 260ish takes quite a while to develop that much mass. With 3 years experience, I don't know if you really put on that much. I definitely could be wrong though. Either you have more mass than we think or know at this point, or you gained a lot more fat than you think and your friends have been stroking your ego a bit. With some pics, we can make a better assessment as far as that goes.
Post up your typical diet, specifics, total cals, macros. We can give more detailed advice concerning that when we know exactly what you are currently doing. And how long have you been reducing cals up to this point?
No worries, you came to the right place for advice.