That right there worries me.
When you go to the antibiotics, did you know if was bacteria in the 1st place? Gram negative or gram positive? Did you know how long you needed to take the antibiotic for to be effective?
Meh. Most of that stuff is pretty easy to figure out in many cases,
if one does the research. I know of no doctor who does a culture before prescribing any antibiotic.
And I readily confess that I'm quietly hoarding some cipro I was prescribed but ended up not needing last spring. Won't be good forever, but it's handy to have available, although of limited utility as it's just about never a first-line type drug.
There has to be a sensible balance between "nonono, go to the doctor who went to school for a decade to learn how to read that infections in x anatomical location tend to be caused by y type of bacteria and are treated with z course of antibiotic" and "Yay! Mexican drugs! I have some levaquin I can take for my headaches!"
The balance is important if for no other reason than to know that antibiotics are often not effective against sinusitis, they usually don't make much of a difference in severity or duration, and therefore usually shouldn't be treated with antibiotics. Ditto bronchitis, pharyngitis (absent strep), pretty much any non-specific URI. There's always the caveat for "high-risk individuals," which is why I started researching this stuff--I got stuck in the higher-risk category, and got seriously over-prescribed abx any time I went to urgent care instead of the pulmonologist.
Which isn't a big issue--except when other stuff that might be helpful is under-prescribed. Like "take some tylenol, it'll help with the pain." Or hot compresses or using a neti-pot or whatever. Or other types of drugs entirely, if there's an underlying problem other than drippy-coughies.
Or, a little good research is also handy in a situation where someone has caught something from his kid who came home with it "a few weeks ago" and has gone through two complete courses of antibiotics to treat his sinusitis and has had it flare up again twice after completing them. Unless your definition of a few weeks is different from mine, it sounds like you were prescribed "here, feel like you're doing something" drugs. To have a chance of being effective, antibiotics for a sinus infection need to be taken for at least ten days. The second course, after the first once failed, should have lasted at least fourteen days. Give it three days to flare up again and we're looking at this should have been going on for at least a month or so.
I'm going to go with your abx haven't helped your sinus infection because a) It's not an infection that is still bothering your sinuses, but resultant inflammation or b) you have a perfectly treatable sinus infection, but you're poking at it without actually killing it by not taking antibiotic long enough.
PS: I dislike posting this kind of know-it-all post. I really don't, know less than a lot of people here, and don't mean to any snarkiness or pretense at expert knowledge. I understand that z-packs are a whole exception to a lot of the timing rules on abx, and z-packs can be used for sinusitis, although my doctor doesn't favor that route for reasons he probably learned in his decade+ studying this stuff
I'm sure pharmacology will be along shortly with more accurate information. But I'm pretty confident that most of the above is good thoughts supported by decent info, so I'll go ahead and post. Any hubris implied by the tone is hereby disclaimed.