I'm a pantsy-plotter.
I have to allow my brain the freedom to go where it wants to for about 3 chapters. Soon after that, I'll get stuck--like a piece of paper in a whirlpool. My brain whirls round and round looking for a place to go. Hopefully, a somewhat logical and interesting place.
It's at this spot where I usually stop and plot.
Nothing scares me like having a deadline and no plot. Oh, sure. I have a kernel of an idea. I have characters and I can just follow them around taking dictation. But that only goes so far. When I see another two thirds of a book looming empty in front of me, I panic.
Yes, there have been books in which I never, ever came up with a written plot. I wrote Strange Neighbors that way. It was terrifying. But people seemed to love the book. Why? Because it was "character driven."
Romances are known for being character-driven stories. It's important we know what motivates our protagonists and antagonists. After that, we sit down with them--keyboard between us--and ask, "So...what are you up to today?"
Do they always tell us? No. That's when a plot (even a thin one) comes in very handy. If you know your pro/antagonists, you'll instinctively know how they'll feel and react to any situation. Now, all you need is a situation for them to react to! Enter the plot.
A few weeks ago, I was in panic-mode. I took a long car ride to NJ with a fellow writer and we plotted Act II. (I had pantsed Act I. About 6 chapters.) When I got home and made a story board with those plot points on them, I felt oh so much better. Ah... My characters had situations to react to! For a while.
Getting together with my critique partner one day (who is even more of a pantser than I am) we brainstormed Act III of my book, plus Acts I, II, and III of the latest in her series. It can be done! What I think I learned is how vital the brainstorming aspect is. If you're 'missing something' perhaps that idea is in someone else's brain.
Find writers you trust and ask if they'd mind listening to what you have so far and tossing out ideas to give you some forward momentum. Hopefully, you'll get out of that whirlpool before your brain becomes mushy and disintegrates--or your heart gives out.