confused and sad

i need to talk, and no one i know can even begin to comprehend what i'm dealing with. i was adopted at birth, into a family with no other children. i had a pretty fairy-tale life, and i love my adoptive family more than anything. i had an open adoption, and until i was 7 or 8 my birth parents were always in my life as an aunt & uncle. i was always aware of my adoption. when i found out the details of my adoption i was hurt. my birth father had a nasty habit of impregnating then leaving his wives. i have 2 half brothers by one woman, and a half brother & half sister from another. i was put up for adoption, and my birth parents stayed together for almost 2 decades. apparently it was a good choice for them. i cut off contact with my birth parents. they were going to visit when i was 12 or 13, and they canceled at the last minute. i remember being extremely disappointed, then shortly after the excitement i felt turned to fear and i haven't had a relationship with either of them since. i was in contact with my bio-sister and one brother, but he wasn't interested in speaking to me, and i lost contact with her after one of her children died. i didn't know how to deal with the grief i had over the death of a child i'd never met. my adoptive mother is still in contact with my birth mother, they remained friends and now my birth mother wants to visit. I know i should see her, speak with her, hear her out, but it hurts. my whole life i have wanted to be a mother, i cannot imagine giving up a child. i feel guilty for being angry with her. i've always felt that loving them would somehow be betraying my adoptive family. i feel angry for feeling guilty. i didn't ask to be put in this situation. i feel abandoned, i always have. i'm terrified of people leaving me, but i often drive people away. the pain of feeling like i wasn't good enough for my own biological mother is always with me, and it makes me feel guilty because i feel as though i'm cheapening the love of the family that adopted me. and as much as they love me and i love them, i cannot walk into a room filled with them without seeing myself as an outsider. i am so angry, and i don't know who i am angry with. i'm so sad and i cannot find anyone who understands. i feel ungrateful for the life that i have gotten to lead, because in the back of my mind i always feel like an impostor. I have nieces and nephews who have found me through Facebook. my biological sister tried to add me as a family member on some app they have and in response i deleted my whole account. i freeze, i can't think when i'm confronted with biological family members. my biological father sent me a message, telling me that he loved all his children and that i could always talk to him. I'm ashamed to say i responded by telling him that i was not his child. i don't know what to do. part of me longs to meet her, to sit down across from someone and have the moment of looking across the table and seeing something of yourself in someone else. i want to hear what she has to say, but i don't think i'll be able to accept it. most of all, i don't think i could meet my biological mother with my adoptive mother there. i think my head would literally explode. i feel incredibly lost, i don't know what to do.