Help?

I don't quite know what to write but basically i recently found out that my mum has cancer and with this it brought on a whole load of emotions for me and i guess my past came to haunt me. about a year ago a became really close with and older boy he was about 3 years older than me and i trusted him with everything he was like a brother to me. But he abused my my trust i guess and me too for that fact. We went for a walk as we usually would but it seemed as though something had changed within him for the first time things seemed awkward if you get what i mean anyway we sat down and he went in to kiss me but i rejected it and just went to walk away as i thought that he understood me and that i didnt want anything more but he grabbed me i looked in to his eyes and it was like looking in to a strangers eyes everything had changed and yeah. he slapped me and shouted abuse stuff that he knew would get to me as he knew me well and then he did it i never expected it off him but he did and i have never brought my self to say it but today i was told by and adult that i need professional help and stuff and i didnt know how to take it so i didn't i guess until now. he told me i had to tell my parents and i didnt want to as they have enough going on please help me what should i do or say?