Why do you consider 5% high? This is very reasonable.
What values do you have in your Mysql ini file? Mysql reserves memory according to your ini file.
I´m using default mysql index (no InnoDB), my server has 4gb of memory...
The screenshot was taken when the load average was in 2,3, so I´m worried about that
Normally I would suggest taking a look at the output of top or vmstat during high loads, but when you don't feel comfortable with your server I suggest get someone who can manage your server.
That's actually pretty low for MySQL. A database server can never really have too much memory... The more of your database it can store in memory, the faster it's going to be (especially indexes).