first of all- yes, that is rape- and even though you didn't say a thing to him it is not your fault.
however, it isn't as easy as 'tell an adult' and he'll go to prison. the fact of the matter is that a rape trial is no small thing to go through and sometimes women don't want to put themselves through it. if after taking care of your immediate needs you decide that you want to report there are lots of folks who can help you do that. girl, you should not have to feel like you have to bear the weight of keeping this guy from hurting other young women- what you need to do now is take care of yourself. what are you doing to take care of yourself? talking to friends can be really helpful- there are local crisis centers in your area that can hold everything you say confidentially (they won't tell anyone anything... you don't even have to tell them your name) and you can just talk to them about how you're feeling.
sometimes writing, working out, yelling, singing... can help. if you feel like it keep in touch and let me know what you're doing to help yourself feel better. it takes a strong woman to get through this and the fact that you're posting here asking for advice shows admirable strenth, my dear.