Adderral question???

ok so ive been on adderral xr 20 mg for like 3 months now,so yea it does make me more focused on things n stuffs n yea it has got me losing alot of weight..but like now when i take it ,it makes me feeeel really tired ,when i first toke them i was like a roadrunner but now i just feeel tired n weird at the same time...any advice...hlp plz !!