I'll try and keep this short! I am looking for advice on how to express hurt feelings to my friend with BPD without coming across as argumentative and harming our friendship. 

We met 12 years ago. He is my best friend, and we always have fun together and have got each other through a lot of bad times.  We had a fall out in our early 20s, but very much got over it, and have been really close for years since. 

We've spent even more time together over the last two years, and "bubbled" together during the lockdowns. He recently started dating someone and has bubbled with them instead (which is understandable, and I have no issue with) since late December. 

Since becoming involved with his new partner, I've barely heard from him (three phone calls and one half hour socially distant walk since Christmas). We used to speak pretty much every day and see each other at least a couple of times a week. It was my birthday recently, and he didn't call.

Essentially, what I want to ask is how to approach explaining my feelings are hurt, without creating unnecessary conflict or being accusatory?  

Our friendship is one of the most important things in the world to me, and I consider him family. I really don't want to end up pushing him away more, and I am scared he'll be defensive, but I can't pretend not to feel discarded. 

Any advice is massively appreciated!