Sorry to hear about your panic attack, it must have been a very frightening experience for you. Also that you still feel uncomfortable driving on motorways - that can't be good for yourself or others.
Last year, a neighbour of ours (mid 40's) had a panic attack at a set of traffic lights of all places! She just sat there unable to move on & had to phone her son to come & drive her car home for her - she hasn't driven since.
She does get very frustrated at having 'given up' as her car is still sitting her garage! I've been trying to encourage her to have refresher lessons to get her back on the road again & she is 'thinking' about it.
Maybe you will benefit from having the same for motorway driving, etc.
Good luck.