Yes I Have Severe Pain And I Am Taking 7.5mg/325

Yes I have severe pain and I am taking 7.5mg/325 hydrocodone. Generic for nor o and I was wondering how long the medication would last if I took 2 nasally and took 2 orally because there only 7.5mg which would be 30mgs and my doctor said if I get in severe pain I could take up to 4 at a time but I would need to wait at least 6-8 hours to re dose but don't re dose 4 of them just re dose what the bottle says? Could you help?