I don't think that you're stupid Danie14. This is hard stuff The recipe for leaving is not as simple as just deciding to cut all ties and going, it's more complicated than this. You may also be feeling a lot of stress with his behaviors and this may weigh heavily on your mind? I can related with feeling isolated and distressed in my marriage with my wife's behavior's and not know which way to turn because we had our kids.
He's being super sweet right now because he sees you all good or split good. He views the world as a threatening and malign place and what he fears abandonment - real or perceived. It's frustrating and disappointing when we display our commitment and reassure that we won't leave our partner and that's assuming that their fear is reasonable. That said, a person suffering from BPD has an unreasonable fear of abandonment and he's being "super sweet" to deflect possible abandonment.
You know it's coming and you may notice that your pBPD is becoming unstable, emotionally blackmailing you, being hyper-critical, twisting things around and projecting their actions on you and using "never" and "always" statements and your faced with rage. I can relate and most times I engaged in circular arguments and tried to reason with logic with someone that has a distorted belief system.
Have you checked our article on taking a time out? I understand it may be difficult when we're in the thick of emotional blackmail and fog and it will help you with coping. I hope that helps.
TOOLS: how to take a time out