Though not as serious as yours I've suffered from mild OCD since my teens.Mine is mainly to do with my fears of impurities and catching sicknesses. And I can understand how you must feel then. The paranoia and restrictions we put on ourselves can often drive us to depression too. And my OCD caused me to get a seemingly incurable eczema too which is not a good thing!
Personally what helps me is,honestly, my faith in my religion. I often read up on how nothing can happen except by God's will and pray a lot,take some necessary precautions, and then try my best to get on with life.Its not always easy but at least I know I'm better now than sometime back,Al Hamdullilah.