A year ago, i was treated for a klebsiella sinus infection, now i've been diagnosed with a frontal sinus staph infection. is this common/normal?

No: This is quite unusual. Either there is something amiss with your immune system, you have had chronic problems with your sinuses, have been treated with too many antibiotics, or have some other unusual problem. Sinus infections, when bacterial, are commonly due to the normal flora of the nasopharynx (pneumococci, strep, hemophilus, and so on).