Severe sinus headaches

The nasal decongestant medications (especially if it's a nasal spray) and the "D" (also a decongestant) in the Claritin-D may be giving you re-bound headaches. I know it's really difficult, but decongestants should only be used for a short period of time. When they wear off, your symptoms come back worse than before.

Try using a Netty pot, saline spray, or those tablets that dissolve in the shower and release eucalyptus and mint. A hot shower may also clear your sinuses. Once the decongestants are out of your system, you may actually feel a lot better because you've broken the rebound cycle. Give it a couple of weeks.

If your symptoms persist, go to your doctor. You may need a prescription allergy medication or a nasal spray (not a otc decongestant one). Personally, I've found that a combination of the two works rather well.

The allergy tests are good to either avoid what you are allergic to (or in my case, find that I cannot really avoid what I am allergic to--dust, grass, outdoor mold). They are also useful if you want to go on and get the allergy shots. I wouldn't consider those until you find out if different medication will work.

Also, try switching to hypoallergenic or at least mild products, such as soaps, detergents, lotions, cleaning products.

I hope you feel better. And remember to only use oral decongestants when you really really need them and only for a couple of days. Avoid decongestant nasal sprays all together. They're just too addictive.