What I don't understand is how I could not be bothered by these things all my life, and now suddenly they completely rule my life.
Awakening...first, welcome to the forum. This is a good, safe place to be.
The quote above is something that I can really relate to. It took me almost 30 years past my initial trauma for it to come to the surface and demand my complete attention. I felt the same way that you do. You might find that as you dig and delve into your traumas that you'll find other points in your life where the PTSD has tried to push through, but you were able to suppress it through various means.
BTW-what you've written makes perfect sense. There's a lot of folks here who understand where you're at and why you feel like you do.
Again...welcome.
Lisa