The sleepiness& headaches should lessen.
Take the Wellbutrin after you eat food & take aspirin or Tylenol for headaches. I think the irritability may just be the way you are feeling from the shift in the meds though I don't know the time frame of the switch.
Call your MD 1st thing Monday AM & tell him/her that it's an emergency. Tell MD all your symptoms. I'm assuming you're taking Wellbutrin XL which has less side effects.
Hope you feel better soon