I absolutely get that feeling! (And the good news is, reading more will indeed help!)
We also have book clubs here on WaniKani, there is the [Seeking Nominations] Beginner Japanese Book Club // Now Reading: 骨ドラゴンのマナ娘 (they read manga and books) and the Intermediate Japanese Book Club // Now Reading: 怪人二十面相 (Jan 4th), and you are strongly encouraged to ask questions regarding the understanding or anything, really, in the club threads. Even if you read a past book club pick, there will still be people around to answer your questions (or there are similar questions and answers already).
The Intermediate Club is now in week 4, so you could try and trail behind the club if you want, and maybe catch up even at some point? 
Or just pick a book that interests you. That’s really the most important thing to make you stick with it 
That’s a good goal to start with, and then you can see how it goes and adjust accordingly. I’m sure you will be up to speed in no time.