Ashamed of myself.

How did I not know I was pregnant? I went to the doctor today because I have the IUD and they did a pregnancy test on me because when they mentioned my last period I told them it stopped about last year in April. They weren’t concerned because it’s been doing this since I’ve been young, I’m 29 now. Well I am 17 weeks pregnant have not taken ONE prenatal vitamin and I’ve been crying because what did I do to my baby, I didn’t eat good I drink and eat so much sugar because I’m trying my best to gain weight and that’s the only way I’ve found that works. I feel like I’ve failed my child and I’ve given it a brain defect or something. Anyone have any similar stories? I’m desperate for someone to tell me it’s okay. Also I have NO symptoms what so ever. Crazy crazy crazy.