Sadness associated with my growing belly? Venting.

I'm 20 years old and I'll be 21 when baby girl arrives. I've always been very tiny my whole life. The biggest size I've been is a 3 and before the pregnancy and for awhile during I was a 00. Well, as soon as I hit 20 weeks, my belly has truly emerged and that has brought a lot of feelings. I've only gained one pound so far in the pregnancy, so the only thing that's getting bigger on me is my belly. Ladies, the other night I cried my eyeballs out because my pants wouldn't button up anymore. It feels so strange to try on things and there's a big belly. And to not have my clothes fit anymore is so devastating!!! Idk why this hurts so much because it's to be expected during pregnancy but I'm so hurt. I feel so big now and I don't like this feeling. And that makes me feel even more awful because I love love love my baby but not my body. All I do is cry about this!! It makes me so sad.