I had this exact same problem- miserable everyday. Sinus pressure and headaches everyday. Tylenol did absolutely nothing, so I went to Target and invested in a somewhat cheap humidifier.. Literally have not had sinus pressure or a headache ONCE! It has been a miracle worker.
It could just be congestion caused by increased blood flow, which is very normal. As far as the suggested sudafed, I would avoid it. Typically it has been considered safe, but it hadn't really been tested. I read a recent study showing it could be linked to a higher risk of certain health defects in the baby, especially when combined with Tylenol. My doctor said not to use it unless absolutely needed.
If it's lower sinus infection a saline nasal rinse is great. Upper sinus infection, friggy flip turn is great. Meds weren't addressing the root of the infection in my upper sinuses, but the flip turn got that nasty infection out
Do you drink milk, eat ice cream or yogurt?
If it's not an infection, dropping dairy from your diet may greatly help. Dairy's a notorious mucuous producer at times in some people, and part of your discomfort may be from surplus mucuous production causing sinus pressure. Similarly, avoid excessive sweets.
It's safe to take Sudafed or Benadryl.