Mine got out of control when our basement flooded. There was already lots of extra stuff there because our boat had just sank. Everything needed to be washed. There was so much that I didn't get it all ironed or sorted. Then I couldn't climb stairs. It's still not all done.
So, sit down, take a deep breath. Sit there for no more than 15 minutes and decide how you want it organized. Maybe yardage pieces (2 yd & up), wide backs, smaller pieces (1 yard or less) by color and/or by category (I had Christmas, Cats, Music, and I recently separated out kids quilts (suitable for kids under 10 or so). Then go away, and decide how much time you want to spend on organizing. I would suggest 10-15 minutes at a time. Then once or twice a day spend that much time organizing. And while you're organizing, separate out those fabrics which you really don't want, and give them away. It can be done if you look at it a little at a time. And agree with yourself not to buy any more until you've made something entirely from stash.
My stash is still not really well organized. But I just pulled out enough blue fabric (and lights) to make a quilt for a wedding in a few months.