Nyjah,
I was thinking about you and Sheena last night, and I want to add a few things to what I said above.
I suggested that at 13 both you and Sheena are too young to be sharing information about your abuse, because the emotional burden would be too much for either of you. What did I mean by that?
When a survivor tells someone close to him, he is taking a big risk in two ways - for himself and for the other person. If the other person takes it badly or says things that hurt the survivor, he will feel betrayed and shamed and it could cause him big problems. The other person, at the same time, may not know what to say. She may suddenly feel responsible for the survivor and wonder what should she do to help. Or she may feel awkward: is the survivor weird? was it his fault? why didn't he run away or tell anyone? can she trust him? etc.
These are huge emotional burdens for ADULTS, and in your case we are talking about a 13 yo boy and a 13 yo girl he likes very much. Like I said, I am not talking down to you, I am just stressing some plain facts that have to do with age. Would you see yourself able to make all the funeral arrangements for a member of your family that you really love? Of course not. The emotional burden would be terrible. And the reason would be your age. We have all been 13 bro.

There is a time for everything.
Here is something else to think about. The abuse you suffered IS NOT YOU! It does not define who Nyjah IS! It is a terrible thing that others did. It defines THEM, not you. When you withhold this information from Sheena you are not denying her vital information about who you are and what you are worth as a boy. You were so terribly hurt - okay. Does that make you less lovable? No. Does it make you less able to feel and care for Sheena? No.
One thing you CAN do, Nyjah, is talk to her honestly about issues like sex and touching, kissing, feelings and whatever. Ask her how she feels about you not being ready for sex yet - it's nothing to be ashamed of. I know from our other conversations that you really like Sheena and she likes you, and that is so cool, so very special. Why not tell her that you like her as Sheena; you're not like the boys who just look for girls with sex in mind? Let her see that even though you aren't ready for sex you, as a boy, really feel things for her, as a girl. Tell her that if she were not ready you would still want to be with her and share other things with her - like the dance tomorrow - and you hope she feels the same way about you.
Want to know something bro? Anybody can have sex or fool around. But it takes some special chemistry and strength to share feelings and trust each other. That will be a stronger bond than just sex could ever produce.
Much love,
Larry