I'm about to be 14 wks and I haven't gained a pound.

I even have been using an app to make sure I'm getting enough calories. I feel like I'm full all the time and so uncomfortable. I eat every couple of hours to keep from getting sick and keep my remaining morning sickness under control. Even though I'm eating tons of calories I actually keep losing weight or staying at the same weight I was when I got pregnant. I work 40 hours a week still as a cashier at Walmart. I'm trying not to worry but is this ok or should I be telling my doctor? What's weirder is my baby bump keeps getting bigger but I srsly haven't gained anything. This is my first time and it's frustrating to be full all the time and uncomfortable with no actual results.