You seem to believe that there are three states of mind.
1. I believe.
And that makes sense to you?
Yes, though I don't know could be replaced with not being aware, though whether or not it is a state of mind is dubious because can something that you're not aware be a state of mind when it does not even exist in your mind? But yes, if you're completely unsure of something you can say that you don't know, as your knowledge isn't great enough for you to lean to belief or disbelief.