It’s more likely than not that your teachers kinda sucked. I found that very little of my English and literature education prior to undergrad taught me much about what literature even is, let alone how to interpret it.

If you’re interested in expanding your mind, there are plenty of resources you can do it with, but it might be best pursued under some sort of tutelage. If you’re particularly self-motivated, you can pick up a book on literary analysis (I recommend The Critical Tradition: Classic Texts and Contemporary Trends) and read about the history of literary criticism and analysis. But be warned—the reading is not easy, and some things will likely go over your head or remain indecipherable. Derrida is a mindbending trip and Lacan doesn’t make much sense to even the most advanced readers on a good day.

Otherwise, I’m sure there are some YouTube classes on literary analysis (see if Crash Course has any!) or find some classes at your local community college!

Honestly, even reading through the Wikipedia pages on literary criticism and literary theory would give you a good starting point. You can start learning about the various approaches and schools of thought, their strengths and weaknesses, and figuring out how you can apply them to the stories in your life. As you dig deeper, you’ll start to see some of the big names cropping up, and if one particularly interests you, there are tons of PDFs that you can find online.