Hopeless and a failure

I have never really had any friends my whole life. Ive dealt with depression and ocd for 4 years, suicide idealization, i just graduated high school last year and now in college. Still no friends, i ruin my everyones life. My 21 year old sister does not love/care for me. My mom.. Most of all i have hurt her and stressed her out all my life. My dads gone and i wish i could have died with w/ him. I mess up everything i do. I am selfish, weak, and a person that should have not been born. Im 18 years old – a female . Currently on 3 meds and currently goes to therapy. I fake my smile so ppl think im happy . I have a boyfriend for 3 years that i have hurt and does not belong to me because he deserves someone much better. I have considered suicide for such a long time butim too chicken to go thru w/ it only because im scared of messing up and living with brain damage/ missing limbs. Etc.
I dont know what to do and ive always felt i would die by suicide