I don't know what causes writer's block but I would guess any sort of "block" probably relates to anxiety about ability to XYZ. Such as with your drawing ability.
Perhaps consider the mindset of writing for the sake of expressing your idea, not so much creating a really good book.
What were you looking to express in the first place? What sort of ideas? Was it a weird, creepy town full of creepy people? Was it a calm scene that suddenly erupts? Whatever it is, look at some successful ways this was expressed.
Try writing without planning to publish it. Just set yourself 15 minutes to write at full speed. Even if it is nonsense.
Let's say I want to write about a dungeon with a warrior, and I start:
Draplach wasn't your average warrior. He was very thin, short, and drunk most of the time. Why was he a warrior? Well, his mother told him he would never amount to anything - which inferred being a warrior - so he made it his life's mission.
After twelve years of hard work he'd finally managed to scratch out the level 1 classification. Everyone in his party was either or nine years younger, but about the same size. He made sure to shave so none knew how old he was.
Bla blah. He fails immediately people start laughing...
And continue just stream of consciousness. Not aimed at publishing, nothing, just relinking your brain to your hands, and to typing. Avoiding pressure, and refocusing on the pure joy of taking thoughts and putting them on paper or computer - regardless of accuracy or craft, just the act of it.
