How do you deal with paranoia that limits your ability to function?

My PTSD stems from experiencing the very traumatic events surrounding the death of my first child. For years afterwards I was constantly afraid that my other children would die, afraid to the point where I would check on them every night, multiple times, just to make sure they were breathing. Gradually this has improved to the point that I can go weeks without this fear.

A year ago I broke my leg and it coincided or triggered a severe bipolar depression swing. After a rough few months stuck inside I found myself paranoid about driving anywhere, especially long distances, and generally afraid to be around people. There has been some improvement with the being around people, but I am still struggling with driving. I am constantly afraid that anytime my family or loved ones take a trip anywhere they will die in a car wreck. This weekend I have an opportunity to go and enjoy two of my favorite pastimes, but the fact that I may have to drive two hours by myself is crippling and terrifying me to the point where I want to just bag the whole trip. Stupidest thing is that I used to drive cross country alone on a regular basis, logging a tens of thousands of miles without any fear or worry.

I guess I'm just wondering if anyone else struggles with similar issues and how you have managed to overcome the paranoia and fear. Thanks.