Have you a bump yet? if you haven't really yet, then maybee your inards are getting squashed earlier till the bump allows more room. My bump is not notticeable unless you know, and my appetite has really gone down in this last week, as I think my stomach and the baby/ uterus are fighting for the same space till bump/tum goes out, and I'm only 18 weeks. Are you quite small / short too?
This should get easier