2009 Ford Mustang v6 4.0 transmission

I own a 2009 mustang, it has 197,000 miles
and recently the overdrive light has come on
and started blinking, also when I was driving
home that night it was shifting really hard and
eventually it wouldn’t shift at all once I got
down my street, so I shut off the engine and
towed it the rest of the way home, I would like
to know what is causing it to do so, and how
to fix my issue because I love my car.