Continue with your doctor(s). Consider switching to another GP/PCP, or another ENT (or see one if you haven't, though I assume you have).
Sometimes you need a long course of antibiotics (on the order of 6 months) to rid yourself of the infection, and of the proper type.
Though, while your stress probably has alot to do with your immune system dysfunction, you should also take a good look at your environment and life over the past 6 months or so. Have you moved? Any new pets?
Any change in diet?
New supplements prior to the infection?
Things of this nature.. it could be anything .. sometimes what is perceived as a chronic infection that won't go away has a pathology locally. It will be where you spend alot of time, so your work needs to be considered as well.
I understand how frustrating this is. It could be worse, I promise :)
Try to get your vitamin D from the sun. That is to expose yourself to it at least 5 days a week for 5-10 minutes and that is it. This is enough to make 50-60,000 IU's and not damage your skin. This is far superior than a supplement... but the supplement is fine. I assume you are taking on the order of about 1000 IU's of D3 a day.
You do have a high/normal WBC .. which is just more confirmation of your infection, with the sinus scan -- your doctors should really be on top of this -- I think you need to consider getting a 2nd or 3rd opinion, with a fresh set of eyes and ears .. get your scans, and medical records of the last 4-5 months at least. So you will have easy tests to bring to whomever you see, this will save alot of time and money. (Getting your records may cost a few dollars, but is a good idea to have for your own safe keeping in the first place. )
There isn't anything I can tell you over the internet to do .. I won't tell you not to see your homeopathic doctor, but don't spend a fortune there if you can help it. I know you are desperate, but analyzing your environment and using modern medicine you will be able to get to the bottom of this. This is an infection, is not hidden, and has all classic signs - this should be able to be taken care of with the proper medications over time -- Even a combination of steroid with antibiotic may be necessary but only for X months.. it isn't a permanent thing.
Do not consider surgery,.. this is an isolated acute event that has run too long -- you can utilize some methods of removing some of the build up of mucous in the upper sinuses if you wish to help the body rid itself of the toxins/build up -- but don't have any of the invasive sinus surgery no matter how desperate you are. An ENT May eventually push this, but hopefully you can clear this up fairly soon.
Good luck,