You said you are self-studying- to what / to whom are you committed? It’s not too late for you to switch to a different history (or art) subject- and for that matter as you are at the Grade 9 level, there is no need or particular advantage in having it be an AP. One of the best things about homeschooling is that you have the flexibility to build an individualized curriculum, but it’s also important to build a strong base for future studies.