My kids almost always get stomach aches with
strep infections (that is when they culture your
throat with the swab).
Many viruses will also cause stomach issues such as nausea. On top of that, when you have a virus, you often aren't hungry and then blood sugar drops, the stomach gets irritated, etc. and it can also cause stomach issues. Coughing until one gags is common and once you gag, then throwing up is much easier.