My answer:
I don't ask enough questions. The ones I need to ask more of are the emotionally difficult ones. I don't ask them because they're emotionally difficult. It also doesn't help that the last time I had a big set of such questions, and I tried to ask them, it repeatedly ended with me being emotionally destroyed.
It's making me quite a bit more cautious in my current relationship. But he's a great guy and doing pretty much the opposite of what the last guy did, which helps a lot. He lets me approach him at whatever pace I want, and doesn't seem to get too terribly upset if I'd rather keep my distance. Which then makes me want to come closer.
And then sometimes I wonder, if I'd done with the last guy what my current guy does with me, maybe it wouldn't've worked out the way it did. Live and learn by watching others with more experience I guess.