Boyfriends past calling

So my boyfriend was in a car accident 7 years ago... The thing is his girlfriend back then died on his lap in the car that night... But now he's constantly dreaming of the accident (I think the main reason is because her  parents won't let go and still takes him to court after all these years even though he wasn't driving his nephew was )so he'll randomly start shaking and next moment he sits up straight. because of this he doesn't sleep well at all ... I offered to take him to maybe like a therapy session but he doesn't belief in that at all ... What can I do to help him it breaks me toe see him like that because I know it was a very tragic accident