AITA for getting the wrong idea (i have to make the title long)

I feel absolutely awful and i regret what i did

Imma keep it short An old girl friend (not ex of gf) needed a place to stay over The thing is we had to share our bed (edit2: i told her we had to sleep together) I was fine with it till she took her pants off and i got the wrong fucking idea and u fuckin know what my second head told my hand to do (edit: SHE EVEN SPREAD OUT HER LEGS OK?)

Anyway she left to my room mate and they talking

Dude i feel like shit cuz i got the wrong fucking idea and i feel absolutely disgusting and perverted PLEASE DONT JUDGE ME I ALREADY FEEL AWFUL AND I CANT TAKE MY MIND OUT OF THIS