My Husband Had Back Surgery 2 Days Ago, We Are

my husband had back surgery 2 days ago, we are home, he is taking oxycodone for pain but has been experiencing severe headaches over his eyes and head. he has been drinking lots of water but has got sick this morning and hasnt ate much or been able to have a bowel movement we are trying to find out what is caausing the headaches. He is also on oxygen when he is sleeping.