How can you be honest about your fellings toward another person if you are unsure how you feel?

It sucks to say “I dont know”, or worse to hear that sometimes

Ive got a second date this Saturday and I want to be up front with her, but I am kind of wishy washy right now. It feels like there is more pressure in this dating game as I get older because its more common to be thinking about marriage as opposed to when I was in college. I like her ALOT, but there are some things about her that are not the NORM for me.

Is it wrong to date a person if you’re pretty sure you don’t want to spend the rest of your life with them?