Tryingtoimprove, Hatzlacha Raba! Speaking from my perspective as a mother of a teenage girl I would encourage you to be upfront with all your family members, yes your sisters might call you “frummie” for a while but then they might just join you.
Try to take it one step at a time – socks(even short ones)or knee highs under long skirts.Being from out of town I don’t really get the “opaque” part all the girls and women know(not chassidush) wear regular sheer pantyhose/knee highs. Check out the resale/thrift shops you might have to travel out of your neighborhood & they won’t be “frum” stores but for a few of dollars you can buy some nice skirts.