Stomach pain or cramps for about a week?

Well after having subway last week I've been having these daily stomach cramps on and off every few hours that range from mild to extreme where I can't think clearly for a second and am nauseous . Anyway is this just some kind of stomach flu/virus or something more serious? It's just pain, I don't have gas or have to use the toilet or anything, just plain pain, like a really long, potent stomach ache.

At first it felt like there was a rock rolling around in my stomach but over time that sensation sort of dulled down, anyone have any idea what this is or experienced something like this?

I suppose this is also partially what a girl would feel like when having a period.
Stomach pain or cramps for about a week?
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