Post-Concussion Syndrome vs. Sinusitis/Allergy Headaches

I was involved in 2 snowboarding accidents, which resulted in 2 mild concussions. After the second one, I experienced dizziness, nausea, and difficulty concentrating. The symptoms went away after about 2-3 weeks, but about 2 months after the second accident, I began to have headaches. What was confusing to me was the headache was accompanied with facial pressure, "behind-the-eye" pain, and a headache that radiated to the back of my neck. When I went to my doctor, I asked that she consider sinusitis (even though I did not have the usual thick-green secretions associated with an infection) because she dismissed my symptoms as related to my concussions. She gave me nasonex and zyrtec which dramatically improved my symptoms and then I was later put on antibiotics when I had more definitive symptoms of infection as seen through a CT scan. Now, about a month later, I'm having the same type of headaches which radiate to the back of my neck. I'm now really confused because I don't know if I should think it's part of post-concussion syndrome or if it is related to another sinusitis.