I've got severe cat allergies as well. Nothing really totally helps. There are things you can do to help. Vacuuming with the filter helps some. Having the cats bathed weekly. Not allowing the cats into your bedroom and changing your clothes outside your room so you don't bring allergens into your bedroom. Use a neti-pot to rinse your nasal passages regularly. I also found saline sprays helped some.
There is also a more homeopathic treatment out there, more limited, called NAET that I've had frienRAB who had success with. You might want to search to find out more on it.
Zyrtec is supposed to be the best for cat allergies. I typically took Allegra. I've also found that Astelin also helped me a bunch. I took it in addition to the Allegra, Flonase and Singulair. Also, immunotherapy can help as well. That can take a year or more to really start having a difference be seen. At least that is the way it was for me.
Outside of that, I had to make a choice as to how much I wanted to suffer vs. my love for my pets. Not an easy decision. I lived with it for years, then I developed bad asthma with the allergies and decided my health was priority. Immediate family took care of the cats though.