What you want is a language model. This will give you the probability on a word by word basis.

Something like [1] is pretty much state-of-the-art. It's worth noting that the kind of writing you are doing change the probability significantly. [2] shows this quite well.

[1] https://colinmorris.github.io/lm-sentences/#/billion_words

[2] https://colinmorris.github.io/lm-sentences/#/brown_romance