IPhone automatically changes certain words to random words?

On iMessage, some correctly spelled words will autocorrect to really random things (mostly just capitalized the entire word) I once typed. For example,
Nevermind changes to NEVERMIND
Haha changes to Haha

And it's just really awkward sometimes and annoying to try to change it back. Is there any other way I can disable than turning off autocorrect on the settings?

I think your problem is auto correction
For 4's do what i say…
Setting> general> keyboard
Then turn off the auto correction an check spelling.
It is all i can do… Sorry if it is not work…
xoxo