Someone help?

Im 16 weeks pregnant. I never wanted to be pregnant, im only 22 years old but it happened. Because of a little mistake i made i now have a baby on the way. everybody around me is so happy for my pregnancy my boyfriend is super excited fo be a father. Its the first grandchild and everybody is so happy that they forget about how im feelling. 
  I couldnt be feeling worst. I cry all the time, i have no one to talk to, all mu friends that are moms told me they felt their life change when they found out they were pregnant. So why it didnt happen to me. Why i dont feel this change and this happiness im supposed to be feeling? Why i dont love this child that is growing inside me? Am i the only one who feels this way? Is there something wrong with me? I dont know what to do, i dont wanna go out anymore  im ashamed of how fat im getting idk what to do anymore