I really really need some tips on how to deal with this, I'll appreciate anything!

So... About a 6 months ago my stomach started acting weird (mostly diarrhea) and I was since diagnosed with IBS. Everything stays in if I take some imodium (diarrhea medication) so I have been living off of that whenever I go out lately. However, I skipped it once last week because I was feeling fine, and I almost shat myself in front of my friend. We had to run to find a toilet and it was really embarrassing. 

Yesterday was the first time that I went out since then, and I took the pill again because I really don't trust my stomach. However, just before I got to the store I could feel my stomach move and I had a full on panic attack (I have had these before as well and they're definitely connected to my bowel) I had to run through the store because I was so scared I'd need a toilet. By the time I got home the feeling was gone (didn't need to poo) but I was just crying and shaking from the panic attack. 

I'll have to drive 12 hours next week because I'm moving. I notice that my anxiety about my stomach problems have got noticeably worse and I'm already panicking about not shitting in the car. I'll be travelling with 2 other people and I find it really embarrassing. I'm scared I'll at least have a panic attack in the car if nothing else, just because I'm so scared I'll destroy the car. 

So, does anyone have any tips for this poop anxiety, or panic attacks in general? Any kind of coping mechanisms that could help me get through it? I'm not so much scared of the hyperventilation and such, but I'd rather not feel tense and nauseous for 12 hours in a car, so I would love any advice at all. 

I'm already planning on seeing a therapist once I finish moving places.