Feeling depressed anyone else?

I remember first getting pregnant I was so thrilled and then I learned about all these things that could go wrong in pregnancy that just took the joy out of everything for me. I’m constantly worried my belly isn’t big enough for 18 weeks, or the fact that I can’t feel any flutters at all. Then you come on here and you see all these woman with perfect bumps and feeling there baby, how are you not supposed to get depressed and not think there is something wrong with the baby constantly. I just want to start enjoying this but it’s so hard when you constantly thinking something is wrong with the baby.