So, I just want to know if I am the only one behaving like this: concealing or even lying, and hoping that a difficult moment will pass by quitly?
You're not the only one - all of us have had to do this to avoid going through yet another meltdown by our BPD partner. We can see the very predictable crisis coming so we try to diffuse the inevitable by any means we can, even if it's not the way we would like it.
We're caught between a rock and a hard place; if we point out our partner's errors it only inflames them more as, in their mind, they're never wrong but if we constantly cover for them and go along with their wrongful ideas then we're not being true to ourselves and that's no way to live. Plus by pandering to them we're actually reinforcing their beliefs that they're always right.
It can be very mentally draining as we constantly analyse our actions, trying to decide if we've said or done anything - however innocently - which might set our partner off. Truth be told, we
never know what will annoy our partner so we have no chance anyway.
I remember I stopped telling my exBPD that I was going out with my friends because she would instantly class this as 'going out looking for someone else'. It makes us feel as though we really are doing something underhanded when we know we aren't.
As for discussing things, I rarely got the chance. We weren't living together and after a meltdown she would just stay away for weeks until she decided she didn't like being alone and would come back looking for me.
In the end it all comes down to how much you're prepared to endure and how far you're willing to go just to keep the peace. As I said, all the pretense puts a huge mental strain on you. In the end I stopped trying to peace-make and just let her rage if she thought I'd done something wrong but I knew by then - after 4 years - that the relationship would be ending as I wasn't prepared to live life like that.
So you're definitely not alone in what you're going through.