Trail maybe you have tried these things but... just in case, since I have to drive a lot for my work (three and a half hours daily on average, sometimes four or five) I thought I might share a few tricks I have that help me feel safer...

I almost always have my gps on as a safety net, except for very short and familiar trips, so if I dissociate I won't be lost. It also helps me stay present to keep an eye on the screen. For the longer highway trips, no matter how many times I've done them, if I try to just drive by memory, pretty soon I am very far from where I started with no clue. I get frazzled and confused and then the near-accidents happen because I am distressed.

I also have music on-- hum along, keep the noisiness in my head at bay.

On extremely bad days I try to have something nutritious or low calorie to chew on, just another thing to keep me from disappearing, different flavors and textures. Jerky, a weirdly flavored gum, dried fruit, etc

If I do none of these things, before I know it- no idea where I am. It's crippling and I feel like I shouldn't be on the road. But in combination it works for me, and I somehow manage the massive drives ok.