It sounds like she could be on the edge of a condition called bloat
www.marvistavet.com/html/body_bloat.html
If you do not soak her dry food before feeding it you might want to do that.
You might also want to change her food to a high quality one and split it into two meals a day not one. I say a higher quality food as often dogs are sensitive to grains like corn or wheat, or to soy in their diet and swapping to a food with minimal ingredients like California Natural (just one example of many good ones) can help a lot.
Yes you should be concerned and I'd try talking to your vet about the symptoms you see too.
Hope this helps you!
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