Doctors, what's wrong with me?

Hello, I will try to explain everything as precisely as possible.

It all started on Tuesday (today was Sunday) with lunch at McDonald's. I didn't have much; just a burger, small fries, and a Coke.

After I finished eating the burger, I started to get a slight stomach ache. I didn't think anything of it and went to work.

Over the day, the stomach pain became more of a stabbing pain, whether when bending over, sitting or kneeling (standing was possible)

It was unpleasant, but bearable for the first day. By the evening, I felt very unwell, had a fever (38-39°C), and my stomach pains were getting worse. All I could do was lie there, since I was in a hotel. So, I didn't have any pills with me.

The days passed, and every day it got worse. The feeling of weakness increased, the stomach pain became more unbearable, the headaches took over, and finally, on Friday, the climax. Neck pain, pain when coughing, a strange feeling in my chest, my heart beating faster than a Formula 1 car can go, my fever was at 39.3°C… the only thing that went away was the stomach pain. Despite treatment at home, neither the fever nor anything else I'm describing here went down.

So, I've had a constant fever for almost a week. If it doesn't get better by tonight, I'm going to see a doctor.

What do you think I have? Please let me know.