I (26F) am in a relationship with a 33 year old man. When it's good, it's amazing. I've never loved anyone this way, and every little thing is just.. perfect. But then his swings hit. I instantly thought of BPD because of how it happens. It can happen in an hour, he goes from calling me his soulmate to pushing me as far away as he can. Saying things like that he wants to die and the only thing keeping him in this world is his dogs, and that I can't or that I am not trying to understand him. That he doesnt have any friends. Nobody cares about him etc. 

We had a trip booked to my home country booked, just for 6 days. Time taken off work, everything ready..2 days before we were should leave he dipped. He is still in his dip and well, we never went. I had to call my mum in tears explaining that we aren't coming. I know this dip won't last though. It's stays maybe tops a week, and then he apologises and we move on. 
I just really want to help him feel better in some way. Does this seem like bpd? Is that something I can bring up (once he is better) or would it be overstepping? I am adamant on making this relationship work as we are quite literally soulmates when things are good, and I want to understand him and work with him to minimise pain from having these dips.