I also have the same - I'm 10 weeks - and it started at about 8 weeks. I find it worse in the afternoon, and my stomach just balloons out. Really uncomfortable, and I've taken to wearing suits to work (no-one knows yet) because when I bloat out I look very pregnant so I need something to hide it. Day starts off fine, but gets worse in the afternoon.

I haven't really been able to pinpoint why. Sometimes I've had a fizzy drink at lunch which may contribute. Other than that - usually have a sandwich. I had been having a latte in the morning, and wondered if the milk was setting me off - I've stopped that recently and it may have eased it a bit. I'll start to try to drink more water.