If you look at the abuse forum there's a sticky with a list of useful threads. One is titled dealing with flashbacks. Maybe going through it will help you. Link is below.
When I am having a flashback and am at home I sit on the bed cuddling a teddy bear. I also take prn afterwards. There's nothing I can do but ride it out. I tend to panic though if I am out and about though.
I am leaving gentle hugs if wanted because I know how debilitating they are. Mine are sa related so I talk through it with my friend who has also been SA but it's not an option available for everyone.
Have you ever sought professional help for the reason behind the flashbacks?