I am sorry I overlooked your post earlier, your situation is much the same as mine. I don't know what the situation for you legally is, but I know where I'm from my wife actually isn't allowed to move out of the province I'm living in unless I give consent. With our situation I am allowed by law to see my son. First thing I would do is speak with a lawyer in terms of understanding your legal rights to your son, nobody other than the courts can prevent you from seeing him.
Your ex is a completely different story. If she doesn't want to be around you she doesn't have to be. I was lucky in that mine wants us to be on good terms for the sake of raising our son, but every situation is different. If you haven't done so already you should do some reading on boundaries. Your ex has boundaries that you must respect, if she doesn't want to speak to you, or see you, that's her right, you can't control it. You can only control yourself.
What are your plans for recovery? Are you seeing a therapist? Have you been officially diagnosed? Are you on any meds? How long have you known you had BPD?
From what you have said, you want to be a good father. Is that motivation enough for you to get the help you require? Having children when you have BPD increases their odds of having BPD by 6 times. The stats go from 2% to 15%. By getting the help you need you can help reduce this number and be a better father for your son.
I don't know your situation, I don't presume to. One thing my wife had said to me was that she was worried to have her son with me. Now that I'm getting treatment she doesn't have that worry anymore. I'm not saying it will happen in your situation, but it may help you.
I read what you posted in my welcome wagon thread... it makes me happy to think that someone could benefit from my words and my experiences. I have a few more threads I'm working on with this board, I'll post links at the bottom. They are basically tracking my progress and helping me keep motivated to the road of recovery. It's something you could try as well, take whatever approach you see as best.
The Kuro Journal -
viewtopic.php?f=18&t=12691Kuro's Homework -
viewtopic.php?f=7&t=12696Here is the link to all of the homework that ash has put on the website (that's what I'm doing in the homework thread) -
viewtopic.php?f=7&t=12334Also be sure to check out the tools section on the left hand side of the board. Finally I'll give you a website that I haven't really looked at yet, I found it a bit overwhelming at first and haven't gone back... but it's dbtselfhelp.com.
There are a number of resources out there to help you, we are here for you.