I have been fighting nasal allergies and sinus problems for over 25 years and I've learned a few things. First, allergy injections help very few people and they can make you worse. The idea of injecting you with the things you are allergic to (in order to make you immune) is kind of an oxymoron. The last time (I've done it 4 times) I did the immunotherapy, I had injections twice a week in the doctor's office. I was to call if I had any reaction such as swelling, redness, and heat in the area of injection and the approximate size of the irritated area. When I called to report "all of the above," the doctor's office was asked if the size was closest to 1/4, 1/2, or 3/4 inch. My "irritation" was 2-4 inches in size. The nurses were shocked; the doctor said I must be exaggerating and had me stay after the injections so that it could be verified. The nurses measured the size of the reaction area and it was 6 inches! The doctor still felt I should continue for a year. So I did. After one year, I asked the doctor "What next?" since I had shown no improvement. His answer, "You've improved."
Since then, and especially lately, I am hearing a lot about how allergy doctors don't know what they are doing and there is no evidence that immunotherapy helps. Let me clarify that I am not slamming allergy doctors as not knowing what they are doing; apparently, there is no known effective treatment for allergies and NO doctor knows how to treat them.
So the point is, unless you are lucky and start improving, you may be wasting your time. Get a second opinion from your regular doctor, if possible; you might also see an ENT doctor. According to my doctor, ENT's are the specialist of choice to treat nasal allergies and sinus problems, not allergy doctors who are going to prescribe immunotherapy and antihistamines and nasal sprays to everyone.