Hi kee-
I'm sorry you have and are going through all that; your story sounds completely common around here, and the fact you found this website and it speaks to you is really all the 'diagnosis' you need; it's not the label, it's the behaviors that matter.
I felt like I was living on a roller coaster with him and that he never took our marriage seriously. I was planning children and kept asking him when we could look at starting a family and he would not commit. In the end he told me he can't imagine having kids with me.
Borderlines have an unstable sense of self, meaning who he 'is' to himself is constantly changing, and that has a ripple effect into how he thinks and how he feels about everything. Trying to be in relationship with that is just like being on a roller coaster, as you noticed, and that's a roller coaster that never stops, the only way to get your feet on the ground is to get off.
Now I want to find a way to let go of him, and his empty words? The words he told me this year was so 'pleasing' to my ears I just didn't trust them enough to take him back.
Good for you! Borderlines are all about attachments and the fear of losing them, and if he fears he will lose the attachment with you he will launch into sugar, idealizing you, until he knows he has you of course, then it's back to devaluation, the perpetual push/pull of the disorder. You've steeled yourself against him so you don't trust the words now, and consider that progress, even though they still touch you emotonally.
How can he not see that is very cruel to tell me, who had dreamt about having a family with him (I actually believed he was the love of my life and the person I would grow old with), that I should be in his life and see him when he has 5 kids with someone else? On the other hand he tells me if his gf acts in a way that he doesn't like then he will change gf's. His favorite expression is that "there are always more beautiful girls in the sea".
If yours is anything like my ex, he's not malicious, just clueless. It's a combination of stunted emotional maturity, the disorder gets in the way of 'normal' maturation, that and borderlines are in a lot of pain, which puts them in survival mode much of the time, unable to consider other people's feelings, too busy dealing with his own. And throw in the defense mechanisms of cognitive distortion, projection and splitting and you will never get your needs met sustainably there, you probably noticed.
Now I have cut contact with him, but his words still haunt me. I really need a good way to realise that even if he tells me he has changed and is a family man that those are just that - empty words.
But I am having a hard time to let go of "the what ifs". What if I had taken him back again? Would it have worked? Those are the thoughts that keep haunting me these days. Even though realistically (and statistically based on past experiences) it would probably have worked for about a year before he would tell me "eff" off.
The words will continue to haunt you for a while, and the key is to stop them coming, which you've already done, but you don't get over a multi-year relationship with someone with a personality disorder overnight. You may find that that's the good news as you detach, because the constant focus, that will lose it's power over time, can be the inspiration to dig deep into what's going on with you, an exciting time, and you may come out the other side amazed at how much you've grown and how differently you see yourself and the world. It's a brand new day! Take care of you!