Almost 19 weeks pregnant and still don't feel pregnant

On Sunday I'll be 19 weeks pregnant but I don't feel pregnant. I had an ultra sound at about 8 weeks and everything seemed fine with the baby then. Then at 12 weeks I heard the heat beat and it sounded strong and healthy. At about 15 weeks I heard the baby's heart beat again and it sounded strong and healthy. I'm scheduled for another ultra sound on the 30th hopefully I can finally find out the sex of the baby. But every time I go to the doctor I'm afraid they're going to tell him something is wrong with the baby. This is my 3rd pregnancy and I've had 2 healthy babies so far. I don't know why I feel the way I do. Why I'm so afraid that they're going to tell me something is wrong. I know I'm severely dehydrated and I'm pushing the water but it's not really helping. Every once in a while when I'm sitting down trying to relax or in the evening I might feel little flutters in my stomach but I don't know why I feel the way I do. Any help or advice would be great thanks.