Firstly, I am so so sorry that you had to go through something like that.
Its going to take a long time for yo to ever be "ok" with what happened to you. It is totally understandable that your boyfriend just wants to help you, and he probably doesn't know how he is going to help you either! He probably wants to go and find the guy that did it to you and beat the living day lights out of him. It's probably a case of, I really like this girl, how could something this bad have happened to her, I can't stand the fact someone would even DO that, let alone to anyone I care about, I dont know what to do.
You say you never dealt with it at the time, which is understandable. But maybe it is time for you to face it? Did you ever report what happened? Maybe you should. Maybe it would help you to "deal".
If you really can't stand talking about it all the time with your boyfriend, then you need to have a talk to him, tell him, that you never dealt with, it, you are trying to deal with it, but him talking about it all the time makes you feel uncomfortable. That one day when you are ready, you will be able to talk to him, and reassure him that when you need his help you will ask for it. He just wants to be there for you by the sounds of it. I know it must be hard but you should let him. Maybe you could tell him that now, right now in this conversation if he has any questions you will answer them. It will be hard to do sweetie but it might help put his mind at rest. And if you restrict it to this one conversation, and ask him not to ask you again then perhaps you can both start to move on.
I really hope this helps. Take care.