Flashed at the bus stop, what can i do to stop the nightmares?

it was like any other day and i walked to the bus stop. I had done this for a year because the bus didn't go down my road and i had just moved there. well One day I heard a whistle and every time i looked around and stopped looking i heard the whistle. it gave me chills. the next day i walked to the bus stop by myself and a man came out of the house and he pulled down his pants.and flashed me. I was scared, but i put it off as he might of been drunk and so i went to the bus stop again but i brought my brother, but he had to go home and get something and i was flashed again. i just turned around and cried. he was aggressive and yelled at me to look and If it wasn't for the sound of the bus coming down the street i think he would of came across the street. my bus driver asked me what was wrong and i lied and said nothing. i never went to the bus stop alone again, but my brother told me that the guy had been watching through the window. i refused to face that way and watched the pinned up goats. i didn't stop going to the bus stop, because i didn't want anyone to see i was scared. my best friends the only one who knows. ever since October I've been getting scared by little things and been having nightmares. The guy even road his bike down the road a couple of days after my last day of school. when i met up with my best friends that lived 6 hours away i acted happy and out going and had fun no one noticed that i had been troubled only hours before. What can I do to stop the nightmares?