So last night I had tacos for dinner and had an upset stomach almost immediately. (I think they were too greasy) when my stomach hurts it gets crampy , but I had a little bit of gas, then it was fine. But since last night, I feel pressure on my lower stomach. It's okay when I am sitting, but when I stand I feel the pressure or lay a certain way I also feel the pressure. It doesn't hurt really, just uncomfortable. Is this normal? Could it be my uterus growing? I'm a first time mommy and am about 13 1/2 weeks. Just nervous and want to be sure it's nothing serious I need to consult my doctor for. (I do have an appointment tomorrow)  Any advice would be greatly appreciated!(: