Sinus infection headaches are notoriously difficult to cure completely. I have been troubled several times since spending so much time in Texas. Having said that, I think my UK dentist infected me and it spread up one side and was really bad for a week or so.
The point being, two separate courses of antibiotics didn't really help. The third did. When it reoccurred a year or so later, one doc said Tetracycline has to be the one, and I had the script filled with an alarm bell ringing.
Years ago, (1980) tinnitus had started after a course of that, and I didn't take it this time around because of the link. Almost at the same time the headaches vanished and I felt much better, so that issue was never addressed.
It seems that when one has it once, there is a tendency for it to reoccur. I've described on this forum about hanging over the bath trying to get saline water into my sinuses. The relief in the past has been instant - once I can force the stuff into the cavities. You can hear the squelching, clicking and popping if it goes in. Then sniff/suck like hell to get it out again. Upside down, fill head, and blow. I even get it coming out of one tear duct. Don't know why only one.
Sterile warm water, about as salty as the sea. After several tries it usually starts to work.
Spasms after infection.
If you're like me, the body seems to react to being attacked by certain muscles going into spasm. If it becomes a real problem, ask the doctor if you can use the dreaded Valium AS A DIAGNOSTIC TOOL ONLY. It works miracles as a muscles relaxant, but is as dangerous as hell to people that get addicted or have major kickback when it wears off.
I get (almost) uncontrollable rages, after even minor irritations. It's not allowed in our household in more than one tablet at a time.