That’s not to say, you completely ignore the possibility of there being someone else.
My advice would be not to ask, especially if you know that you will not be able to handle the truth.
Unless she brings it up, or you find out from reliable sources that there is someone else, I suggest that you keep the focus on the the two of you.
It’d be nice to know that what you had was too special for her to just move on so easily. the last time you got “too personal” things ended badly (your own words).
Of course that’s no comfort for you, but it’s the reality of being broken up.
You asking her if she’s seeing someone else or interested in another guy could mean two things 1) you’re jealous (and if that was a problem in the relationship before then it means you have not changed) or 2) you’re putting pressure on her when she’s not ready (and that could cause her to suggest you don’t see/contact each other again – at least not now).