about boring part, when you get bored, try the subject that you like.
I love maths and whenever i get bored, I start solving maths questions, because thats not study for me.
And about solving questions correct after a day or two means you don't concentrate while solving them for the first time. (as you can solve them later on, it means concept is clear)
Try to focus properly.

2 parts to the answer:

1. The brain works in funny ways. What you experience is called an "A-ha" moment. The brain is actually working in the background (like a daemon process) even when you are not conscious (aware) of it. So what happens after 2-3 days is that the brain has already evaluated it and then you get it like magic

2. Boredom part is because your brain is telling you that all the stuff you are reading is not important. That is the only thing that triggers the brain to feel "bored". The best way is to take short tests of 25 questions per topic. Still better take sets of 37 questions in Quant and 41 in Verbal. Try to simulate an actual test - and keep goals for yourself. Tell yourself how would you do it if it was the real deal. That is way more fun than just solving questions one after the other.

Hope this helps. Let us know if this works

Arun