I've had 2 colonoscopies, although I was out when they took place I still did the prep. First time I had Picolax and it was okay, taste wasn't as bad as some other preps and yes I did experience lots of D, however it wasn't so awful as I was in the hospital right by a bathroom.
Second time I had Kleenprep - it tasted like sea water and the volume was huge and it was very effective. Again stayed by the bathroom at home all day, then when I went to bed I put old towels over the sheets just incase and used a pantyliner too. Same for the next morning in the car, luckily though no disasters everything was fine. Although everyone feels safer taking these precautions.
Honestly you'll be fine I'm sure, it is a worrying time but it's not as bad as you think it's going to be, I was the same but having gone through it twice I wouldn't be concerned if the third time came around. It's not such a long procedure, risks are low and you'll be recovering in no time. Take care, hope it all goes okay.