A bit of short background: I went through a mentally exhausting relationship, breakup, and hoover period with a pwNPD, and it really fucked me up. I spent months just fucking around with guys and not wanting a serious relationship to build my self-worth back up and have fun without getting hurt. 

I have since met someone I have insane chemistry with and enjoy spending time with and despite my best attempts to not have feelings I have developed them anyway, like massive fucking feels. So now my brain is starting to glaze over and trying to make me either be super short with him until he hates me (which physically hurts me to think about, he's been so nice to me), or to just ghost him and never talk to him again (which won't work because he's in my friend group). I was hanging out with him tonight and my brain randomly decided to flip a switch out of nowhere and I said I had to go and just shut down. One of my friends had to call me and distract me because all I wanted to do was flee. 

But I really like this guy. Like, more than anyone, I think. I have no idea if it'll ever work out long term, but my brain doesn't even want to give it a fighting chance. I've sabotaged every potential relationship, or even just casual stuff, since everything happened so I don't know how to not sabotage. I don't know how to get my brain to not say or do something stupid when it gets scared. I feel like this could be a good opportunity for me to be vulnerable to someone and tell him I'm struggling with it but I feel like it's too much. So my only option is to shut my mouth and power through it, but this is the one impulse control issue I can't seem to conquer, so I can't do that either.

TL;DR How do I not say or do something stupid to ruin something good I have going right now?