I think its important for you to realize that you can be 1,000% tznius without going crazy and without going overboard. If you take on too much before you are ready it will only backfire. Trust me, been there done that.
I think its great that you want to improve in Tznius afterall as woman, this is a Mitzva special to us. But you cant move to quickly or you will get burned out and resentful.
“Up until now I wore a uniform in school… but changed into a short jean skirt and bobby socks the minute I hit the front door)”
Do you realize what a big jump going from short skirt/short socks to long skirt/tights is? Would it be easier if you try taking more gradual steps?
Also, if you feels that you have to hide it from your family that is just going to do more harm than good in the long run. Tell them about what you are doing and get them on board, you dont have to feel like you are carrying a burden alone.
Hatzlocha!