counselling bring back flashback

this all started 2/3 years ago when i was staying in psychiatric hospital due to depression and suicide attempted. i always have a love-hate relationship with the wards, there's no privacy in there , yet it is the one place i know i will be safe. during a week leave from hospital ,i attempted to 'escape' from it by hiding and staying in my friends place on the last day i suppose to return (it all sound a bit 'out of it' but i didnt care by that moment )i was raped and he sent me home afterward . i suppose i was in shock or for some reason , (i didnt remember everything ,infact majority of it ) it didn't really hit me until after the morning of the next day , my behaviour gone completely downhill then esp the first few day . but eventually i calm down and wasn't affect by it.

yet since about a 6 month after the incident , after the news of my friends' death and a book on abuse (my sister bought the book ) , i started to experience flashback. i avoid anything that will remind me . i would keep showering until i feel clean again , anything.

as i am studying psychology , traumatic topic as such will be discuss in class and i had always react badly on them .
i would bunk off class until i think it is 'safe' again . if it is even remotely mention , i would lock myself in the toilet (where i sat down and no one can see) .all sort of behaviour.

After a discussion with my mentor at university , she advice counselling to me
i eventually agree to it , but since then my mind been unsettling.
I just started my first councelling today.
we barely even talked about anything , all i mention is there's was a sexual assault incident.
but the whole day it just kept on going in my head , flashed back kept on occurring , i feel so dirty .
during mentoring session ,i had a flashed back , lock myself in the toilet , crying and shaking uncontrollably.
i thought time is going to make everything better , but from what it look like ,
there's no way out of this.

I feel so small and powerless .
i asked to leave after my mentor come and get me ,
apprantly she was been saying my name outside for a while but i was too in the 'flash back'
i havnt told her anything and just said i am okay when i leave .

i felt really stupid and i know it is partly my fault .
i know if i avoid everything related to it , i prob would be fine .
but i am really exhausted every time after a flashback or breakdown and i dont like that .
i dont really know what to do anymore .

sorry for ranting .