Pinkypeach, it must be difficult to sort out what fears you brought with you versus what fears this new relationship aroused in you. Of course, you have been tramatized, and your "survival brain" isn't going to allow you anywhere near something that could result in the same painful outcome as the XWH caused.
Many would say it's all because the new relationship developed too soon after your marital trauma, a trauma that you will need to work on healing. However, I have a different thought for you. Think of the spectrum of colors as being like the spectrum of personalities of men you know. Do they sometimes seem to all fall in the same range?
To be more specific, if you describe your fear feelings in this relationship as uncomfortably familiar, could it be that something this new BF is like, trips that trigger? Just an unconscious "recognition" thing?
I ask this because, after my divorce from my first husband, I moved on and never met another man who reminded me of him for years and years...until I met my current husband. Right away with him, I remember that "familiar feeling" I got about his ways, even though he looked nothing like my XH. It wasn't conscious, but it wasn't a "positive" feeling, either! It was like "This man might be another version of my XH, maybe?" Since I had zero reason to identify that similarity in him, we dated 4 years, married, and then just a year or so after, darned if he didn't start doing the same kind of sneaky porn stuff the way my first husband had! He is a sex addict and was too ashamed to ever admit to what he was like, so how could I have known? Well, my gut picked up the signals, but I brushed them off as me being a little paranoid. Yet looking back, that "familiar feeling" stuff was my survival brain trying to spare me a lot of new pain!
You also probably wanted to see him hang in there not just give up that easily. But don't discount the reasons you weren't feeling safe, either. Best of luck.