LV Koopa
Jester from Hell
I definitely need to brush up on my Discrete, I feel like I missed somethings there.
Could also be your teacher. My professor was good in some ways (exams were tough but if you passed you for sure knew the stuff), bad in others (introduced topics, didn't teach much in depth and you had to figure stuff out on your own).
Also, discrete math isn't really one type of thing but a bunch of distinct topics. I'd say if you are comfortable with graphs, sets, and the math of probabilities and combinations you are solid.