Sorry if it's TMI but I'm desperate!

It's 1:30am and I have an exam at 2pm today. I've had diarrhea all afternoon (think I've run to the bathroom maybe 5 times in the past couple hours) and really bad gas (trapped gas as well so stomach pains) and my exam is 2hours 30minutes so I don't want it to cause problems during it. I really need to sleep but it's keeping me up as well :/

I think it's because I had really greasy food yesterday, I usually don't eat much fat/grease at all but I'd run out of my usual food and the only thing I had was frozen veggie sausages and onion rings and my student hall oven always sets the alarm off so I fried them and it was super oily. I usually never cook with oil and the only fat in my diet comes from actual food like nuts or avocados or chickpeas etc. so it was a bit of a drastic change and I felt sick after it.

It's just very runny, a pale brown/yellow and my gas smells really bad. I've not eaten anything else that's too greasy but my diet has got pretty shit with my exams and not having time to cook properly, I usually eat really well so I'm not used to this. I don't think I've caught a bug or anything because I don't feel sick in any other way at all.

What can I do to sort it? I'm freaking out because of my exam I really need to sleep and my mum's asleep so I can't phone her for advice.

Thank you