I'm pretty sure

While proofing the latest version of White Lies, my mystery novel, I discovered that I use "pretty" A LOT..

He was pretty sure.
You hit your head pretty hard
It was pretty bad.

Damn. I didn't even know I was doing it. So, I looked it up in my Thesaurus and realized, oops, it's slang. Pretty means beautiful. What is my definition that it can be used in all the ways I use it? It pops up at least once a chapter. YIKES. But I think it must be one of those invisible words (like said or the) because none of my readers called me on it.

What  adjective can I replace it with? And for those purists who say not to use an adjective, bear with me while I get to my point.

"Pretty" seems to be an anything word for me.

Let's look at the first usage: he was pretty sure. Dropping out the "pretty" changes the meaning. Because he wasn't sure. But saying "He wasn't sure." Doesn't have the same feel. Almost? Fairly? About? Just doesn't work as well.

The second usage is somewhat opposite. You hit your head pretty hard. "Very" isn't right. "Almost" won't do it. "Reasonably hard"? Only a socially-challenged TV nerd would say that.

And the third: It was pretty bad. I suppose "very bad" would do, but it still doesn't have the right feel.

There are way too many "prettys" in there and each one is going to be a puzzle to replace. I need to spend an evening with my dictionary and Thesaurus.