Happened to me before, that's why i stopped stashing all of my stuff on just one external. I spread it equally between several now.
There are basically 2 options:
1. Seek professional help at the cost of money and privacy.
2. Destroy it completely and throw it away.
Then buy several new externals and spread your stuff between them like i do.
Then if you lose your stuff again in the future, you won't lose all of it.
Externals tend to be unreliable so it's important who makes them.
If it's some company you never heard of, don't buy their externals.
I am using Toshiba-made externals now, been having 0 troubles with those for many years now.