he blocked me after 5 years over one birthday?

We were together for nearly 6 years. Talked every day. Shared holidays. I thought we were solid. Then suddenly, less texting, short replies… I asked if something was wrong—he said no. I brought up how he ignored my birthday and poof—blocked. No goodbye, no explanation, nothing. I’m crushed. I can’t sleep or eat. My therapist mentioned avoidant behavior, but still… how do you disappear on someone after years together like it meant nothing? Has this happened to anyone else? #ghosted #relationshipadvice #heartbreak