how to find last word in a string sqlite3

I have values (varchar) with strings. There is a word: John, which repeates within each value at least couple of times.

e.g.

John went to town. He visited his girlfriend. She likes John very much. John is in love.

or.

He went to town. John likes football. John likes icecream.

Now I need dynamic solution to find position of last written 'John' within string.

Is this possible?