Upset stomach out of nowhere

[Bluemat]

For most of the last week I've had constipation. If I have managed to go it's been hard to pass.
Today I've been fine. Had a cheese and onion omelette to eat whilst out and salad. Within a couple of hours of eating it I've had an awful bout of diarrhoea more than once. I feel slightly queasy now.
Im not sure if it's the heat or a digestive issue I have been diagnosed with ibs but I've also just been diagnosed with a yeast intolerance so I have cut yeast out of my diet the last few days. Or could it be a bug?

How are you generally eating onion? I have an intolerance to any food within the onion family. Think onion, chives, garlic, leeks etc. Typically within a couple of hours of eating any of these foods, I would have an upset stomach - most certainly diarrhoea - sometimes just feeling queasy but sometimes being sick too. It sounds more of something you've eaten but it equally could be a bug. Do you have a headache, temperature etc?

Stomach upsets are quite common in very hot weather, I expect it's that.

No headache or temperature.
Im usually ok with onion but to be fair there was a lot of onion in the omelette and the salad 😬