I've not seen this angle of BPD splitting bc of another person

[VeronicaL]

Hi! I have suspected that my ex has a milder form of BPD(quiet) in addition to an avoidant triggers. We have broken up twice, the first time over a 'problem', which I am not sure if his realization of BPD as well as  something  else but he said unable to be in a romantic relationship with this issue having a hold on him. HE won't disclose th problem exactly but I believe is this, plus something else. His feelings, love didnt' waver and seemed super upset. We didn't see each other for about 3 weeks but spoke the whole time and eventually at his lead started to fall back into being together without a label, but in essence a couple like before. He seemed really great for about 7 months.  
Brakeup 2- after being away for 2 weeks (Stuck out of the country due to covid) came back over the Hollidays, had a week, really great. Not one indication of anything wrong. On my way out, told me he loves me but he wants to get better and heal and move on from what the problem did to us in breakup 1, (but he seemed more  stern or angry whatever ) and I never gave him the space he needs back then(He never said specifically, I followed his lead. but whatever he asked I gave him! Told me was helping him and loved me more than I knew type things) ..Anyway, he was angry and all kinds of changing the script. Told me no contact, bc what we are doing is making "IT" worse! Not sure what it is but whatever. He kept this in for so long and pretended it was all ok. I was angry at the manipulation. Blamed me for a bunch of stuff but the 1st break very careful none of this is about me. Blamed me that I am happy doing 'this' but he's not continuing to do this after the breakup.  Said space was not asking about the problem and that was abnormal to keep asking NO ONE but me would do that (I asked 3 times ever bc ofc it affected me and our relationship) .I didn't mince words back. IT was short, and I left and it continued on text, and he was angry bc I was calling him out. Maybe not the best thing, but I was upset. YET..still saying he's not done loving me.
Whenever he talked about the problem he said it is not good for the relationship and not fair to me, and if he did the relationship it won't be good for it. The first time in 2 years I felt I understood a 'split' bc he is very sweet, calm , empathetic esp to me. Mad at me for not having anything to say after he blindside me(I was in shock even more this time plus the way he was behaving

NOW--I think the mask finally fell off that night. He has a friend, I'm not fond of, that he is so much better than in all ways. Friend is very needy and had fallen into wrong crowd, fast type people during our time together. Friend always harassed him to do things, but he always spent time w me bc I think he was just not into the types of stuff. Once we were all together about 2 months prior, and the friend broke down, he is drama ish--something about 'togetherness' . Anyway, friend finally got a gf few weeks before we split, which I thought was strange timing. No surprise, friend got dumped within a month.
Now, friend has been pulling mine into going out, staying out, even if just hanging with guys..but smoking weed. Party type behavior, just so unlike mine. This is extremely atypical of mine. My ex had been doing the gym, etc, I believe to get better. I know this bc we have a mutual friend.  

My question-I almost feel that his friend getting a gf triggered my ex (perhaps me being away, us getting very close too). It was like whatever the friend wanted, after 2 years, my ex caved in to him, unnecessarily. Is taht possible that he felt that he was loosing 'friend' to his new relationship caused him to split me?  For example, friend plastered himself and new gf stupidly all over social media w corny things...after 1 month. My ex NEVER 'liked' or acknowledge the pic or the coupling on social media.(the weeks before our breakup).  Which I thought very strange. Yet, in some ways, I feel my Ex is using the friend to get over us and not stay home. I do not think he has dealt w emotions of breakup ofc except brewing about it BFORE he told me anything.

So can this type of thing happen, and is it normal for the ex pwBPD to do behaviors like smoke weed and just behave differently after, like not the person you knew--different personality?  Can another person cause your person to split on you?
It has been 7 weeks today since breakup an no contact and tbh I am still shocked at our friend connection erased bc we were closest to each other.  Knowing my ex, I just really can't believe his behavior to me and just in general..I just feel no way he could have kept a mask on for 2 year?

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[Cat Familiar]

Yes, people with BPD (pwBPD) can change quite dramatically, depending upon who they associate with. One of the hallmarks about BPD is having an unstable sense of self.

It’s not unusual that he’d be unwilling to talk about what led to the breakup, and blame things upon you. PwBPD tend to feel such a deep level of shame and self-loathing that examining their own behavior is very difficult.