Dealing with Nightmares: What Do They Mean?

Past nightmares I have had are beginning to scare me. I constantly wonder why they had to be about that certain topic and what that could mean about my mental health or what my mind fears. The last few nightmares I have had all include someone either sexually harassing/assaulting me or me being raped.. For some background, I have never been raped, I have only been sexually harassed and was kind of sexually assaulted the other day (a random guy locked arms with me and touched my boobs at a roller rink. he said "Don't worry, I caught you" when I wasn't even about to fall. I was just about to chill in a group with my friends). The last nightmare was specifically one about rape. I saw myself showering, someone coming into my shower, touching me, picking me up, kissing me, and of course forcefully having intercourse with me. A part that stuck out to me was that a very close family friend that I classify as a sister was in the nightmare as well, but all she did was stare at me in shock as I yelled for help. This nightmare—which truly felt like a lucid dream—still affects me today, even though I know it didn't actually happen. I don't even understand why I had a nightmare like that instead of ones I had in my childhood (ones about spiders, a living vacuum cleaner, a random figure under my bed, etc.) Does anyone know what having nightmares like this means..?