Why am I like this (rejection)?

Clinically diagnosed BPD for years. I live 100% isolated. To avoid being disappointed, I consider in advance that I don't matter to anyone.

There's this cute person in the medical environment we're sharing (both are patients).

He stares at me during sessions. He talks to me with big smiles. He remembers my everyday problems and asks about them from one week to another. He seemed delighted that I asked his number.

First weeks: butterflies in stomach. My brain sends "maybe you're finally accepted!" signals.

We exchange pet pictures, I refrain myself from sending a million messages. I ask a random question to get to know him ("what's your favorite..."). He replies, then "what about you?". I reply with 4 short messages, including a GIF.

He only replies with a laughter emoji to the GIF (which was ironical, not funny). Instant trigger.

My brain: "why did you ever think you were accepted? You're rejected. No one cares, get over it; and try to survive while literally everyone around you is accepted."

Why am I like this?

I've been following group & individual DBT with no result.