I am sooo sorry and I can sooo relate! I am allergic to everything airborne, and have fought with my sinuses all my life. The only time I felt good was when I was on shots, and can't do that now while preg or nursing.
Here are a few things I have tired that seem to help minimize the symptoms:
1. Get a Neti Pot! They work really well at cleaning out your sinuses, but the do take a bit of getting used to, and you have to use it every day. See if you can find someone to show you how to use it.
2. Keep taking the nettle, it takes a while to work. Also up your Vit C to at least 1000mg but not more than 3000mg (any more will effect the babies ability to absorb it in the future). I swear this is what helped me get through pollen season without wanting to commit harry carry!
3. Drink lots of water (if you aren't already LOL). And check the humidity level in your home. If it is dry get a humidifier or vaporizor, especially for the bedroom. The drier it gets the more painful the sinuses.
4. you can use essential oils in a difuser or put the oil right in the vaporizer. I suggest Rosemary, Lavender, Mandrin Orange (or Red Mandrine), Eucalyptis, and Peppermint. The Rosemary, Lavender, Eucaliptys, and Peppermint help open up the sinus, and the Mandrine (along with Lavendar) helps with sleep. If you have a good place to get oils with a knowledgable staff you can ask them for recommendations as well.
5. When it gets really bad turn on the shower full hot and go sit in the bathroom with a good book.
6. Oh one more I though of that worked when I had a bad sinus infection. Bring a pot of water to a boil and dump in a bunch of peppermint leaves. Stick your face in the steam and breate it in!
I hope this works!