My Dr Prescribed Dextroanphetomine, I Have Been On It For

My Dr prescribed Dextroanphetomine, I have been on it for 10 years for narcolepsy and I also have sleep apnea....my pharmacy have me vyvanse. I just thought it was a generic so I have been taking it for 1month and the last 2 weeks, I notice instead of taking it 1 time a day I take the new stuff 2 or 3 times perday....is this prescription change going to screw my system up? Are pharmacists allowed to change a Dr orders? Without talking to the dr?