Under British law,what you whent through is rape,no ifs or buts.You said no and thats what no means.Dont blame yourself at all,it wasnt your fault.
This young man if you can call him a man knows he did wrong and was probably expecting a visit from the police the next day because of his despicable actions.I hope you get over this somehow.
I am a man myself but have experienced abuse at the hands of others and i am not ashamed of myself anymore but just angry at myself but i too am seeking help for this 20 years after the fact