honest answer? try it all on.
after your body starts going through changes, it’s going to be harder to judge how things look. i’m so glad your at a point where you are more confortable with yourself - that actually makes me so happy to hear !
like, for me, I know what sizes I am, but I find that if I buy my size, they make my body look disproportionate and strange, so I usually go a size up so they fit comfortably but not baggy. (at American Eagle I’m a 00jean, 00dress, and an XStop. But I buy 0’s and S’s so that they feel better!)