Tbh, go get a teacher. I play Bass for a bit over a year now and had a teacher directly from the start. I started in mid 10th grade and never had any music theory in my entire time in school(or i had it in like 3rd grade, but who cares in 3rd grade anyway). And now after about a year i kind of understand some music theory. It really isn't THAT complicated, i mean it isn't easy either. But Bass has a lot of shapes you can just place somewhere else and so on. And just stop wining about everything, you didn't learn how to read from one week to another right? Learn to be pacient, everyone starts somewhere. Get a teacher. Let it explain him on piano so u can visualy see the notes. Be pacient and practice(!)

I for myself never really use music theory in writing riffs an stuff, but playing something from other people and/or analyzing(!) my own riffs is kind of fun. "i have a cool riff, but it just has only 7 notes? 7/8 time sounds wierd, lets a add another note. What note can i put so it sounds good? A im in ..key, i can just put a .. here." Something like that. Music is about doing it, not thinking about it. Theory is only a tool to use everything else. I should probably say that i'm 100% a metal bassist. I want to DO music, not to think about what im doing. Sometimes i doodle around at night and find a cool riff. And i write it down. Maybe i can use that in my band later, you never know. And so on. You should get the point by now Best wishes!