Is this the flu? Or something different?

Patient: I’m just curious what this could be. I know I can’t be diagnosed online, I’m just interested in some possibilities. I usually get 1-2 sinus infections or chest colds each year that tend to hang on around 2-3 weeks each, and that’s about it. Up until now I’ve never had anything like the flu or anything worse than that.On Dec 5 I came down with what seemed like another sinus infection, it came on a little faster than usual, but it also happened to drop below freezing temperatures outside and didn’t go above 32F outside for a few weeks. I assumed it made this time a little worse, since I felt worse each time I had to go out in it, regardless of how well I bundled up. I lost my voice Dec 9th to the 11th. Surprisingly I rebounded quickly after that, and felt almost better by Dec 13, with just a little residual cough and sniffles.I got sick again Dec 19, or maybe I was still sick, I don’t really know? I woke up that morning with a little sore throat and light chest pain when I breathed in, the upper lungs… but it was still cold enough outside that the air alone bothered my chest to breathe it in. Felt quite similar to the same feeling I had a week before from the chest congestion. I spent a little too long out in the cold putting up Christmas decorations, I just assumed it was due to that making the last of the cold worse. That night, though, I felt worse. I took my temperature, and it read 101.7. I felt very tired so I took some Tylenol and went to bed. Ended up sleeping that night, Dec 19, until Dec 23. I woke up a few times shivering heavily and with a bad dry throat, took my temperature, it read 103.5 at one point. I’d drink some water, take some more Tylenol, and wake up a few hours later to repeat the process. I don’t remember much else.I have post-nasal drip due to allergies year-round, and that gets much, much worse with a cold. Sometimes to the point of waking up coughing and feeling like I’m drowning in my throat from it. I had that going on, from what I can remember, but that was it. No other symptoms that I remember.When I woke up Dec 23, I was still pretty tired, but was no longer falling asleep sitting up. My fever was gone. In fact, my temperature read between 97.1 and 97.8 that day. I rested that day, and got up the next day to prepare for our family holiday activities.Since then, I’ve noticed I’m a little sooner fatigued than usual… I can get to around 5PMish before it feels like I’ve been awake much, much longer. A bit of a congested sounding chest cough, though it’s not too bad, along with some sinus congestion. Lastly, I’ve felt slightly nauseous if I eat anything, though I feel fine prior to that. Right around the same time I feel suddenly fatigued nearing the early evening, I also get nauseous, and it stays until I go to bed. The later it gets, say 8PM to 10PM, the nausea also has a bit of a woozy, dizzy feeling to it. Similar to the feeling I’ve had in the past if I wasn’t paying attention and took too much cough syrup. I also have repeated bouts of diarrhea throughout the day, with no real warning.Again, I know I can’t be diagnosed online. I’m just curious of the possibilities. I’ve experienced the sinus infections and respiratory infections more times than I can count, but the persistent fever that knocked me out for a few days and the stomach issues are fairly new for me. I don’t think I’ve ever been sick with anything that gives me any stomach related symptoms.