16 weeks pregnant with baby number 3 and don't really feel pregnant

Last week I was in the ER because I was having a lot of pain and pressure in my pelvic area. They did an ultrasound and I was measuring at 16 weeks but I should have only been 15 weeks 1 day. They said everything looked fine and couldn't explain the pain I was having. Every once in awhile I still get nauseated and I still pee a lot and have some cravings. But I really haven't gained much weight. I gained a huge chunk of weight in my first trimester. I guess I'm just worried because I'm working full time with this one. I'm working over 50 hours a week. With my other two I was a stay at home mom. I go back to the doctor on Tuesday. I hope he can put my fears to rest and tell me the sex of the baby at the same time. Any advice would be awesome thanks.