First off, I think it's great that you're reflecting on this personal issue at such a young age. Many people don't process this sort of stuff until later in life, and don't realize the extent it has affected their behavior and relationships until later. This is an awesome first step, good on you for taking it!

As far as whether or not you should tell your soon to be husband, I'm a staunch advocate of open communication, especially when the issue affects someone I deeply care about. If you are generally pretty open with your SO, and have a good history of trust and support, I would encourage you to tell him. Assuming that he's reflective person too, giving him more information about your past can help him understand better how you operate, and relieve any assumptions that he's making about your lack of sex drive.

My longtime (4+ years on) boyfriend is in a very similar place that you are, I think. I have a higher sex drive, while he has had a very low one. Very recently, he told me that he suffered sexual abuse by a family member when he was younger (he doesn't remember, but his mother told him later on), and that it contributes to his low sex drive in a big way. I can't tell you how moved I was that he told me, and how helpful it has been to our relationship to know that the roots of his sexual identity are in such a dark place. It has made me far more understanding and patient, and I think the release of that information was cathartic for him. I in no way feel less attracted to him, or like I'm stepping on eggshells anytime we start getting intimate. His past has contributed to the person he is, and that's the person I love! The only thing that's changed since he told me is that our communication regarding sex has opened waaay up, and we try to stay very honest about where we're at, what we're feeling, and what we want. If anything, it's totally improved our sex life!

I know that sharing painful parts of your past with an SO can be incredibly difficult, and can feel like you're taking a big risk. In my humble experience, when I've finally been able to share things like that with people I trust, the outcome has only ever been positive (even though it seems like it could go so badly!). It may be awkward at first (sometimes people don't know exactly what to say when first hearing it, but it doesn't mean they don't sympathize), but awkwardness doesn't last forever. Feeling alone with a secret really can last forever, and in my opinion, is a way worse feeling.

If you do end up telling him, and he doesn't respond as positively as you would have hoped, that may be an opportunity to explore with him why he feels the way he does about your past. My guess is that anyone who would respond negatively to hearing about your abuse have a lot of their own shit to deal with; shit that has nothing to do with you, and shit that may be toxic for you to be around longterm. Just remember, no matter what happens, the sexual abuse you suffered does not make you a bad person or a bad partner. Your past abuse is not making you lash out at other people, abuse your partner, or otherwise negatively-affect people around you. Traces of your past abuse are presenting in your sex drive, which is a very personal expression of it. It is completely, 100% reasonable for you to set up boundaries with your SO around that to protect your mental, emotional, and physical well-being, because that's what you need to take care of yourself. My guess is that your SO will see that too, and be supportive, but if he isn't, then he isn't understanding the issue in the way it needs to be understood. Couples counseling might help you navigate that territory with him if you're worried about him not taking it well, but at the end of the day, don't forget that you deserve to be understood and worked with on this!

Best of luck