They say always finish what you start...

I'm currently about 30 pages through my YA fantasy novel. I had this story in my head for a few years, and decided to finally start writing it. I got past the introduction, set up some crucial elements to the story and finally the kid is in the fantasy realm.

And now I'm completely stuck. I have no idea where to go from here, I can't map out any of the plot ideas in my head. I'm literally trying to combine all these ideas I had into a solid story, and have no clue where to begin to mesh them all together. I went from writing voraciously to not being able to even write another word.

I have another idea for a fantasy novel that I already have mapped out, complete with an outline of the plot, and I am craving to start it.

But I really, really want to finish my original one. I became emotionally invested in it, and the character, but it's just stressing me out ridiculously that I can't think of what's going to happen in the story. It seems too complicated to conjure from what I have so far, but I like what I have so far. I'm struggling to put it all together.

Any suggestions? Should I keep brainstorming the original? Even if it leads me to days with blank pages? Should I start the other one? I'd hate to stop writing my original one, but I'm simply fed up.