Dear Fellow Allergy/Sinus Sufferers: I empathize. Here are some suggestions that have helped me:
1) Try irrigating your sinus to see if that helps. Keeping bacteria down if you are prone to sinus infections will help to prevent one sometimes. You don't do this every day....only if you have a flare up or it can dry you out. I personally like the Neilmed Sinus rinse with the squeeze bottle. If you use the saline packet included, I recommend only using 1/8 packet if you are already irritated, other wise it will burn like the dickens!
2) Try Afrin Spray (Decongestant) for 3 days and COME OFF if its sinus pressure & stuffiness/ or you are getting a sinus infection. If you have high blood pressure, ask doctor before doing this. After using, blow your nose. Try a hot shower and let the hot water beat on your face. Use a heat pack on your face to help relieve pressure such as the sinus Bed Buddy.
3) A sinus infection DOES NOT always show up when an ENT scopes your nose. Sometimes it is hard for an ENT doctor to think outside the box if they can't see infection. Usually an antibiotic and steroid taper is needed for me to get complete relief when I have an infection. Sinus headaches cause migraines with me. You do not always blow out green thick mucous or blood when you have a sinus infection. You can have a dry sinus infection which causes more pain and worse headache. With that said, sometimes it is not an infection, just sinus pressure which can cause facial tenderness, teeth to hurt & headache.
4) TMJ and teeth grinding can cause teeth sensivity, headache and jaw pain and can mimic a sinus infection. I chipped my front tooth from grinding my front teeth and night. My teeth showed no wear from grinding my teeth. Mouthguard from the dentist helped. All of your teeth do not always become sensitive with teeth grinding or bruxism.
5) I have horrible allergies with allergic & non allergic rhinitis. I did allergy shots - they didn't help. I have sinus issues and had sinus surgery years ago due to chronic sinus infections and narrow sinuses. It helped greatly, but, it isn't a cure all nor did it eliminate all of my headaches. I do have a lot less infections and can breathe better. I am grateful.
6) Be careful using things like Azelastine (prescription spray) too often which is an antihistamine as you can dry your sinuses out too much. Same thing if you take an antihistamine by mouth like Zyrtec. I think this can cause your nose to hurt if it gets too dry.
7) Use a cool mist humidifer in your bedroom.
8) I use Alkalol saline nasal spray (Not daily - just whenever I'm really flared up), Cromlyn spray or AYR saline spray...over the counter. I was told by my first ENT that you have to switch the steroid nasal sprays as your body gets use to them. Examples: Flonase, Nasonex, Nasacort, etc.
9) This is my own opinion and was also told this by my old ENT....a little vaseline a little ways up the nose with a q-tip and then wipe excess with kleenex helps with dryness. Ask your doctor about this before trying. You DO NOT do it every day. If you have the nosebleed in the dry winter months, this can help.
10) Pay attention as to if you are clenching your jaw and teeth during the day. This can cause facial and tooth pain. I was doing that and didn't realize it.
11) When washing your face, are you cheekbones, forehead tender? When you lean over do you feel a lot of pressure in your face and headache pain? With me that is a sign of a sinus flare or infection coming on.
12) When the enamel starts wearing down on your teeth, this can cause teeth sensitivity. Not all of your teeth will necessarily be sensitive either. Try a toothpaste like Sensodyne or Proenamel. Steer clear of strong mouthwashes that contain alcohol as this can make your teeth more sensitive.
13) Sometimes you can get fluid in your ear which can cause pain and it sounds like you are in a barrel. This can go along with sinus.
14) Do not blow your nose too hard.
15) Drinking water thins out mucous. Also, something like Guaifenesin helps thin out thick mucous. This is over the counter. Mucinex is Guaifenesin. The Mucinex D is Guafenesin with a Decongestant. If you have high blood pressure steer clear from taking a Decongestant as it can raise blood pressure.
16) Vicks puts out a plug in that is wonderful in your bedroom at night. Vicks also puts out a steam inhaler that you put your face in and a Vicks insert is put in the base. You put your face into the plastic part and the steam helps open up your head. I love mine and use it when I get really stuffy or have a sinus infection. Also, Vicks puts out tablets you can put in the shower floor and when you take a shower the steam opens up your head.
17) Vitamin C to keep your immune system built up.
18) Last but not least, I have long COVID and I have a lot of thick mucousy saliva that I have not been able to remedy nor get a diagnosis on. I get choked on this sometimes at night. I clear my throat a lot. Going to long Covid clinic soon.

Sorry for the length. I hope some of these help in some way. It has been trial and error for me for years. I can tell that I do not have as severe issues as some of you have listed. I am so sorry you are battling this. I know it's frustrating & painful. Blessings, Hugs & Prayers.....