sitting in school bathroom for lunch

so i have generalized anxiety disorder, panic disorder wirh agoraphobia, and borderline personality disorder. i sit in the bathroom for lunch every single day because my boyfriend and my old lunch group from last year have the inch before me. so i don't have many close friends overall but especially in this lunch. my therapist told me i need to go into the cafeteria and ask to sit wirh someone and i've been trying for over a week but i always chicken out and end up back in the bathroom alone. it's starting to get depressing because i've been sitting alone for months but i'm just too scared and embarrassed. Please if anyone has any tips that would be great, thank you.