Sorry that you were hit. Fortunately that has never happened to me. My process is to move to whichever side gives me the best escape route in case someone coming up behind me shows no indication of slowing down. Sometimes the shoulder has plenty of room. Sometimes that's not an option but on the left there's room between cars to shield myself.

I've only had to move into an escape route a handful of times, and in all of those instances the person stopped before hitting anyone or anything But when you're sitting there exposed while stopped, and someone is approaching from behind quickly, it's better to protect yourself from what may have happened rather than regret it later after you've been hit.

I wear a jacket with high viz yellow. There's high viz yellow on my helmet as well. My integrated stop/tail/turn signals are LED. When I brake, the brake light will flash rapidly 3 times before going solid. Sometimes when I stop and someone is approaching from behind I'll squeeze the brake lever a few times to get the light flashing. Especially when I can see they're looking at their phone instead of the road. That seems to help too - but I'm also getting ready to move just in case!