I feel like a terrible person

Yesterday my little sister was born and I felt nothing. Here’s the thing, I’m almost 22 years old, have a 20 year old sister and a 3 year old brother. When my little brother was born I felt so much love and happiness that he was here. But yesterday when we went to the hospital, nothing. I feel terrible about it but I don’t know why I feel this way. I spent the whole night with my little brother last night, showered him with love and treats.. we went to the store picked out the toys he wanted and watched movies until we fell asleep. Today my mom asked if I wanted to come to the hospital since she has to stay an extra day and honestly I wanted so badly to see my mom but something kept pulling me away from it. I think more than anything I miss my mom and this just makes me feel even more distant from her. It’s probably stupid to feel this way since I’m 22 but I can’t help it.