So sorry to hear about your sinus problems. It can be debilitating I know. I'm currently 13 days post-op after a septoplasty/concha bullosa reduction. I had a year long battle with chronic sinusitis. I also freaked out in the beginning and was convinced it cancer (I'm a worrier too!).
At this stage I think put cancer out of your mind. There is no point in getting yourself into a state over a very big maybe.
Just for your peace of mind I've listed the biggest risks factors and most common symptoms of sinus cancer below. The symptoms you mentioned in your post sound a lot more mild than the common cancer symptoms below (that's not to say that what you're experiencing isn't horrible! Believe me, I know how awful persistant sinusitis is)
The biggest risk factors for sinus cancer are HPV, Smoking, Exposure to some chemicals (as in working with them on a daily basis), Radiotherapy for hereditary retinoblastoma.
The most common symptoms of paranasal sinus cancer are:
persistently blocked nose
feeling of recurrent "sinus infections"
bleeding without apparent cause from the nose
progressive pain and swelling of the upper of the face or around the eyes
closing up of one eye, blurred vision, or vision loss
persistent pain in the forehead, the front of the skull, or over the cheekbones
swelling in the roof of the mouth
loosening of teeth, poorly fitting dentures, or bleeding from upper teeth sockets
In the mean time try steam with inhalant oil, sinus rinsing, a humidifier and I found a good high performance vitamin such as Berocca helped with the constant dizziness.
I hope you've found this helpful