I'm just a random writer. I have no training or professional experience. Just a lot of unfortunate events in my life that I feel the need to express via a screenplay. The problem is that every time I sit down to start the first page I choke and my idea is gone. I have a directional problem because I am constantly wondering if I am rambling and/or diverting from the subject. This ends up becoming a series of mentally crumpled up paper.

I have an incredible love story in my head based on true events of my life. I just can't get it out of me because the real life ending is a sad one. I want to write the ending as it should have been to complete that build up of happiness and warmth. I just have absolutely no idea how to construct a screenplay. I was wondering what books I should pick up to learn this art.

Thanks.

Here's a couple that I've read and would recommend.

The Screenwriter's Bible: A Complete Guide to Writing, Formatting, and Selling Your Script by David Trottier
Screenplay: The Foundations of Screenwriting by Syd Field
Story: Substance, Structure, Style and The Principles of Screenwriting by Robert Mckee

the Syd Field book is pretty good in my opinion, taught me a lot of stuff I didn´t know

I really learned a lot form the book Making A Good Screenplay Great by Linda Seger. After reading it I immediatly bought her other book about creating characters but that is more for writers with some experience.
Screenplay by Syd Field is called the screenwriting Bible but it is quite basic to me. I made a website (it's now offline) about screenwring before I read the book and it had the same content only shorter. So when I read the book it didn't teach me a lot.