It's normal to have writers block every once in awhile, because every author gets it.
You don't have to know the ending of a story when you start. In fact, not knowing everything about a story before you start writing will lead you to explore more creative possibilities and will make your story stronger. I do it all the time!
Write about a character that you seem to know pretty well, and then let this character do something that completely throws your book off guard. See where this takes you. 
Every story should have a plot and stories should have a rising action, climax, falling action, and the resolution.
I usually end my books with a cliffhanger, for example if there's going to be a 2nd or 3rd book that goes along with the 1st, then I leave it off with a cliffhanger, which makes the readers want to know what happens next.
I usually get a few ideas for the first few chapters and then leave the chapters off as a cliffhanger. And start the next chapter leaving right where I left off in the last. Make sure to get inspired for new ideas for chapters by reading other books, and listening to everything around you, keeping your eyes open for new ideas. 
I develop my ideas by listening to music because I have a very strong imagination.
Make sure to have a plot in the story or sometimes I write stories that don't even have a plot to begin with. The plot just forms by itself for me as I continue writing chapters. 
Also make sure you know your characters personality traits and what they look like. The setting is important too, point of view (1st, 2nd, 3rd), time of the story, and conflict. Conflict is important to a story. 
~Angels3403
I only own the characters I made: Annabel Lanette Manchester, Bella Nicole (Woods) Manchester, Kelly Michelle Woods, Brent Armstrong, Rebecca Baker, Rose Baker, Scarlet Isabel Brown, Ashley Davis, Mortikiy Robinson, Chloe Dawson, Brooklyn Hayes (Brooke), Logan Glynn, James Franklin, Nathan King, and lastly Boomer Manchester.