can my mom read my texts if i share my apple ID with her through the family apple id sharing plan - she used to read them in highschool and i dont want to do that again

1. Yes, if you share an Apple ID she will be able to access messages, calls, contacts, photos etc... That's what using an Apple ID on different devices is intended to allow.
2. The entire point of Family Sharing is so you don't have to share an Apple ID. In fact Apple IDs should absolutely not be shared. One Apple ID per person. With Family sharing you don't share an Apple ID, you share specific content.
3. Family Sharing allows you to share purchases, a calendar, icloud storage, an Apple Music subscription and a photo album without having to share an Apple ID. So private things such as text messages, photos, contacts etc.. remain private, but other things like purchased Apps, movies, music etc can be shared, and you determine what photos are shared with others, and what events you place on the shared calendar.
4. Each person keeps their own Apple ID, and just has access to shared content.

You should get your own Apple ID. There may be some data loss, but you can minimize it. If syncing photos with iCloud, ensure Optimization is turned off in Settings/Your Name/iCloud/Photos and/or in Photos/Preferences/iCloud. Then make sure full resolution photos are on the device/computer. When signing out of iCloud, if asked whether you want to retain data, choose yes. Messages conversations will be lost if they are addressed to the ID. See the article below for other places that the old ID should be removed. Also set up Family Sharing to keep access to your apps/purchases. Also see Winston Churchill's response in the below discussion

Apple ID – Create

How to transfer all files from one iCloud account to another

 Apple ID email address or password - What to do after you change